I think I might be the only person in the thread who is not dissuaded by the cost or the playing but rather by the act of painting in and of itself. I've tried to start playing 40k twice now and both times I get bored long, long before I finish even a tiny army.
Hell, I came closer with space marines than anything and all I painted was the better part of a pair of tactical squads. Strangely, I painted them as Blood Angels before I even knew what a Blood Angel was. Just seemed like the sort of color a Space Marine ought to be I guess.
I tried again a year ago with Imperial Guards. Finished a platoon that I was rather proud off but it took more than a week. When I looked at what I still needed to do to "play" (several more platoons and a few vehicles), I gave up in despair.
Currently, I'm considering assembling a force and just saying "to hell with the painting" part. Alternately, I'm considering paying someone who likes to do it to paint them for me. Not sure what I'd go with as an army to be honest, which all but ensures I'll never really take the plunge. In fact, the candidates are:
Imperial Guard - I like the idea of outgunning everyone but the sheer number of things and the need to maintain a cohesive firing line likely makes the whole thing difficult to manage against a well played and highly maneuverable army.
Eldar - I like the idea of a force of specialists but they seem like they would be incredibly hard to paint. They are, incidentally, my favorite army in Dawn of War 2 which did more to put them on my list for consideration than anything else.
Space Marines - Hard as nails and incredibly flexible, it seems like the Marines are probably the best force for my purposes. Except, I'm fairly certain that I would end up noticing that most people play as Space Marines.
Inquisition - All the forces of the Imperium at my command seems like a neat idea. Would allow me to better customize an army loadout for any particular game, but I suspect it is also quite expensive and bulky as I would likely end up with far more troops than necessary just to ensure flexibility.
Daemonhunter - same as above but you get the Grey Knights.
Tau - I really like the idea of a highly mobile, hyper-lethal army. I just don't care for anything else associated with it.
Were I to get into the hobby, realizing that my priority for an army is generally speaking one that is powerful enough to force the enemy to react to my actions, yet flexible enough to allow me some ability to account for the unexpected, which of the above would be my best bet? As a related question, is there a resource beyond e-bay where I could get a pre-painted army? What would I generally expect to pay for a pre-painted army (As in, if a particular model cost X dollars, would purchasing that model pre-painted cost 3*X dollars?)