If you only live 3 hours away and are comfortable driving, (and can take a day off from work, if applicable), do it once without the hotel and all that for a single day one meet and judge for yourself. Your question is sort of like asking "in general" how much someone needs to spend on a good car or go on a decent vacation. Everyone has different levels of "bang for the buck" that works for them.
If you can get up early enough allowing for traffic, etc, I'd recommend doing it on the longest meet day, Friday. If that's too early for you to get up without being delayed by rush hour, do it on Thursday when the meet doesn't start until noon, since it has the same closing time (Saturday closes earlier).
My first meet was a single Saturday in April 1997 (bear in mind, I was also new to the hobby then, so I was in "general acquisition mode", not looking for specifics). I drove in in the morning, and drove home after the meet was over. I don't suspect I actually "saw" everything, but I walked most of the large buildings of that time and ended up getting what I thought was a good deal for my efforts. I had purchased a single Lionel N&W Maxi-Stack car from a gentleman in the Blue Hall, he had multiples and offered them at $60 a piece or 3 for $150, IIRC. I bought one on my first pass by his table. I walked the rest of the meet and didn't buy anything else, so I went back and asked him if I bought two additional cars if he would give me the deal since I had bought the first one a few hours earlier. He joked with me a little, and was willing to do the deal. I considered that a successful first York! (I certainly don't recall every transaction I've done at York, but that I remember).
I found it odd you wanted to exclude all the other things like hotels, gas, food, but kept admission in the mix (at under $25, it's not on the radar in the big picture, unless you live right near York).
-Dave
It's all about the experience, meeting old and new friends, and of course, the trains. 
