Hasbro consistently states at BotCon that fans (the ones who post on boards, attend BotCon for the weekend, etc) make up, at most, 10% of their total customers. We are still a relatively minor side of sales to them, and as long as Bumblebees and Optimus Primes are still selling, they will continue to make them, despite how much we may protest.
The issue comes more when hasbro places its bets on a character that flops (eg: RotF Skids), or a minor character that already has plenty of saturation (eg: Movie Ironhide).
In Australia I'd say adult fans are more important (as hasbro AU has stated that Generations sells faster/better than HftD & RtS), but worldwide (which is what Hasbro US cares about) fans are a small percentage.
Yeah - that is a little ridiculous, and is inevitable when your cast of characters is small, but way too weighted on the wrong side. Luckily Transformers aren't quite at that stage yet.