That question is way to vague to answer as everything you asked is so player depedant.
Which "people" say they're to hard to make money?
I mean; ask the top SnG STT player in the world who plays $1k+ STT's if they are difficult to make money when he's raking in 200k+ a year
Games are as soft as the players are. Therefore; what may seem difficult to you, will be easy for a better player etc.
If you feel you're better playing them than cash, then play STT's, everything else is irrelevant, buy-ins, experience, money etcetc all comes in time.