It really depends on where you are diving. Caribbean operators seem to include the tanks and weights in the cost of the dive, and BCs are maybe $10 for the day. This is because nobody, but nobody, is going to fly with tanks and weights, and most people do not like to pack their BC. I should also point out that the operator will schlepp the tanks to the boat. They also have a box of hard candy to chew on during the SI.
However, diving in the Great Lakes is vastly different. Nothing is included, and the boat may only have a couple of soft weights on board for emergencies. Plan on carrying your own tanks down to the boat. We had 18 people and were planning 4 dives on one day; even with carts it took us forever to load 72 tanks. I will say that the snacks have been better in the lakes, homemade cookies and brownies are the norm.
This isn't to say that one style is better than the other, they are just different. Please don't forget to tip for this service! I like to tip the boat crew $10/dive in both warm and cold climes - perhaps a bit more if the service is excellent or if they BBQ lunch.
Finally, remember to hydrate! Don't count on the boat to bring enough water for everyone, especially if the day is hot. I usually stuff 2-1L bottles in my bag.