Im doing 3 sheet cakes for 228 ppl this friday. Im not really sure what i should charge them. Any suggestions?

How big are the sheet cakes?
single or double layer?
special fillings or flavors that might cost you more money?
fondant or buttercream?
Any special fondant or gumpaste work involved?

It would be helpful to know what kind of event you are preparing the cakes for and decide on a per serving price for a total; i.e. 228 X $2.50 per serving.

Yah, as has been said, more info is needed. Definately charge by the serving - & not just for how many they reuested but how many servings you will get from those 3 sheets.
Since one 12x18x2 sheet serves like 54 you must be making them dbl layered to get 225+ servings. But then you will have over 300 servings from the 3.