AI Resorts can have huge differences in price...some examples of this would be because: # of stars, resort size, location, and types of food and beverage (Premium/Top Shelf to basic/generic brands).
Some places offer Weddingmoon packages (Sandals/Beaches) and some have Free packages (Riu) for the number of rooms you have and other such details. Even with that being said, in Jamaica, you still have to pay for your officent and which depends on the resort. If you are looking for a private reception or even a cocktail hr after your wedding.. almost all charge for this. Where I got married a formal reception with dinner in a private setting was $75 per person. A 1 hr cocktail reception was only $15 per person.
You can certainly get past paying for anything for your reception though. You could decide to dine at one of the restaurants they have on the property with your guests. Granted it may not be as private but you can do that.
Have you thought about a resort yet or narrowing your choices down yet?? This would be helpfull as past brides can tell you all about the resort and what the real prices are.