Not sure how much of that is just venting or how much it actually keeps some people at bay but it's pretty obvious some (anonymous people on an online forum, FWIW...) think it too costly.
Only then you'd be comparing apples-to-apples and then you'd see that by the time you've factored in the 24x7 system administration, monitoring, guy-on-standby for when you're on the road and so on that it really isn't that bad.
Of course it will be higher in absolute dollars if you don't factor in your own time and how much that costs, maybe there is even a small premium if you do, but outsourcing has other advantages besides the ones that translate directly in to money, and those can be valuable by themselves (for instance the time freed up).
If you can't make your business model earn back what Heroku costs you at a given scale then that is of course a problem, but if you can't do that then you probably have a problem anyway, and even free servers wouldn't solve that.