The fact that you feel their web page isn;t professional goes to show how good it is for them to have a partner that sells their games. Making a game is probably about 30% of the effort required to sell a game. Advertising, presence and availablity are the other 70% and if you can find a good partner to do it for you its probably worth a lot more than 15-20% of the price of the game.

I'm trying to sell some games now and am letting 60% of the income go to the marketing team.