If the game is balanced, a 'cheap' tactic isn't really a thing even. But when the game is unbalanced, 'cheap' tactics are a problem.
In CS2 you have 'cannon cheese' for protoss (my favorite race) which basically means you rush a probe to the enemy base, and start building cannons at his entrance as soon as possible to stunt his economy and base growth. Only lower leagues see this as a cheap tactic as higher leagues know how to counter it and turn it around in their favor. (cannon cheese makes it pretty hard to get good in mid-game)
Then there's CS, where there is a REAL cheap tactic. AWP laming/camping. The AWP is just clearly the superior gun for both mid and long range fights. Skilled awp'ers are also good with it at close range. It's a mostly 1-shot-kill gun that requires a lot less aiming skill and tactics than any other gun. So yea, the awp is basically overpowered in most maps. Which is why it's cheap to only use that gun.
There was also the problem with WoW in end TBC. Resto Druid + Arms warrior. The two had perfect synergy in 2v2 pvp and were clearly the superior combination to any other. Once again, an overpowered tactic basically.