This is bad any way you look at it, but it's a situation where the lack of details makes things seem a lot worse than they might actually be.
The description of the incident brings to mind dark images of the kids being sold to organ harvesters, perverts, or bordellos. In reality I'd guess that the situation was that the kids went onto the adoption black market, where parents without kids buy babies and children to raise so they don't have to go through the whole adoption process, or can claim that the kid was their own to begin with. There are plenty of women all over the world who birth a child every year just to make money.
It's possible, given that this is Asia, that the couple didn't know what they were doing was illegal. Raising children is hard war, a lot of young parents wind up wanting an easy out, and if someone offers them one, the temptation is going to be there. If the people brokering the sale and making the offer are official enough, I could see someone falling for it, a couple of dumb kids overwhelmed by being parents being offered money to solve their problems, along with legitimate seeming people who promise the kids good homes... well yeah.
I'll also say one other thing... and don't take this the wrong way, while Asia/China is popular with a lot of the world right now due to them offering cheap goods and the like, not EVERYONE views them as being intelligent. In general most Asian countries tend to be fairly unpopular in the US, excepting Japan which is almost another state given that we have it under occupation despite the political fiction that it's an entirely independant nation. We have the place covered with our military bases and it's our major foothold into the far east. Weeaboos hate that point, but the bottom line is we have a gun to their head 24/7 and despite apperances of independance and some economic back and forth, they pretty much do what we want when the chips are down. Due to all the military prescence there and US tourism, we've influanced the culture heavily, lead it to becoming one of the more progressive parts of asia, and tend to view it a little more positively despite World War II within our media.
Other asian nations like China represent situations where you have massive disperity without the country. On one hand you have huge, modern cities, with everything you'd expect in the first world, and a core of well educated people who run the show. In other parts of the country you've got degenerate rural wastelands where The Middle Ages never really ended for all intents and purposes, and things like "Deliverance" probably seem like progressive visions of the utopian future. You have everything else in between of course, but the point is that the situation is far, far, differant from the western world.
In general your average Asian from a nation like China is going to be an uneducated, easily manipulated bumpkin, compared to the rest of the world. The worker class like this couple was probably from aren't all that well educated, and are intended to be easily manipulated so that when China decides it wants to clear all the "unsightly people" from the streets in order th host the olympics the resistance is going to be minimal.
One thing about international academic surveys, oftentines showing how far nations like the US are behind other nations, is that rarely do we ever see a fair, overall comparison. Generally speaking most nations, especially from nations like China, send their best to represent, where nations like the USA respond with more of an average. Our public school student might wind up faring poorly, but he's generally up against one of the educated elite from one of these nations. They don't for example pick up some dude from a knee-deep rice paddy or one of those underpaid factory workers and say "represent us". We have people equivilent to that in the US (where there are some reaaalllly backwater people) but not nearly as many of them as you see in countries like China where they represent the
backbone of their society. This might sound offensive or politically incorrect, but to be honest you can't sit here and talk about "super smart asians" and reconcile that stereotype with exposes on the plight of the Asian factory workers, where the entire issue is those billions of uneducated people being crammed into inhumane working conditions to churn out cheap goods, for the benefit of the handfull of elite people at the top. Reading articles about those sweatshops and stuff over the years (with photos and so on) is incidently where I get a lot of my information that I formed my beliefs here from.
I personally think that in nations like the USA we take our educational system for granted, as a result when you see first and second generation immigrants from countries where the people aren't educated (irregardless of what comparitive studies might say) they wind up valueing it a lot more highly.
At any rate, the point of this rant (and thank you for reading) is that yeah, I could see a pair of young Chinese parents, who probably work in those kinds of factories and sweatshops if that amount of money was a lot to them (to make this worthwhile) not knowing that what they were doing was illegal. Heck, from a lot of what I'd read I'd guess your average person in China doesn't know what most of the laws are, and is kept ignorant of the laws intentionally. It sounds alien to people in nations where every citizen is educated to understand certain basic rights, and gets a run down on concepts like due process in school as soon as they can understand it, and probably picks up some basic knowledge from well researched TV shows that are legal dramas (not enough where they don't need a lawyer, but enough to have a solid grasp of the basics of what police/judges/etc... can do). For someone in a nation like China, they might not have that kind of basic knowlege, someone who seems like they are in authority tells them "this is okay" and they will go along with it.
What they did was bad, but it might be possible to understand how this occurs.
Do a keyword search for "Chinese Death Vans" or "China, Mobile Execution Chambers" you'll get a lot of hits. Remember this is a nation where the goverment has produced vans that are basically snuff studios on wheels. To the world they claim that the idea is to have the vans go to prisons to do the executions outside, which of course makes no sense (major security issues... it's just ridiculous). As some of the articles will point out, the claims are that the communication equipment is to verify the executions are conducted humanely, however the allegation is that what they are actually doing is "arresting" people, using the comm suites to conduct a trial by remote on someone strapped in, execute them after the "Fair trial" and immediatly harvest the organs so they can be brought to hospitals as quickly and fresh as possible. Basically they are legalized organ snatching vehicles. One of those "too terrifying to be real" things that actually is real... and the fact that the goverment gets away with this down there without some kind of popular revolution (beyond the smaller uprisings we've seen) says a lot about the condition of the people and their knowlege I think.