Most charter “yachts” (which is what you are looking at if you want a “party room” have a beverage license of some sort (either beer & wine or full service liquor… either way, this prevents them (the boat’s owner or Captain) from allowing you (passengers) from bringing your own booze…
The only “charter” boats I know that allow this are unlicensed (party-boat fishing charters) which some allow you to bring your own food.
Now, having said that… If you want a party with a 100 people, and you want booze and food… you can expect to pay around $4,000 for a 5 hour charter… (give or take some $ depending on your location).
I seriously doubt you will find anyone that can allow you to bring aboard your own alcoholic beverages…
Happy & Safe Boating!
Capt. John

me and a group of friends had a yacht party for graduation it was a very nice yacht so 2000 each between us was 8000 for everything foood drinks etc and it held a little over 100 ppl

It depends on where you are. Here in Baltimore we have the Princess Pintail, They charge $3 to 8K but it’s very elegant. so check out their web site or google “Princess Pintail.” it should give you some ideas. Good Luck!

Depends where you live and you have not stated this, therefore no one can answer your question.