5.50 sounds very low. I don't even do burgers and dogs for less than 7 bucks a head.
Your costs include meats, sides, buns, condiments, fuel for the grill,
ice, plates, napkins etc. It adds up.
My concern would be how hard you'd work to cook 3 different times,
plus the cost of keeping all that food safe in between.
Add up all your costs, then think what it's worth for you to do that.
Yeah it may be fun, but it's very hard work. The cleanup is what kills
me. I'm tired, I've got to pack, go home, unload, and clean up the
stuff.
If your costs were 500 bucks, your profit is up to you only.
If you'd do all that for 300 bucks, just add that on. If you need more,
ask for more.....it's your choice.
Keep in mind health regulations and insurance liability. If you don't have
insurance, which costs about 600 bucks a year around here, you could get sued.