I staff most of the cons I go to, which comp the hotel and usually at least one meal (in one case all three in one form or another). For these, about $100 is usually all I need.

I try to do Anime Boston and AnimeFest. AB runs me back about $600 with all expenses taken into account, AnimeFest in 2017 cost me about $1500 (most of that was due to flying out of PWM instead of Logan...but the lack of TSA line was soooooooo worth it. Booking my flight in July probably also played a major factor).