Cheaper ticket prices do not make more people come. They give off the impression that it must not be very much or the owners think it sucks so it much suck and it isn't worth the gas money to go there or worth the extra burst of energy required to go and do something.
2500 to 3,000 SF can be very nice, you simply install smaller more detailed rooms, with as many as 20 little things going on and attempt to have something or an actor every 12 linear foot or so. No long hallways headed to somewhere where nothing is happening. As many as 45 actors or one guy with 45 different masks. It can still be considered to be quite something. I wouldn't go below $10 a person. It simply takes people so long to react to so many well developed things that it might take half an hour to get through and you have not stopped the groups to give a little skit or anything like that. If you actually walk through at a normal pace with no interaction might only take 2.5 minutes.
You are saying parking is an issue? That will prove to be the limitation of how many you can have show up. You have to have people there so long and have enough parking for them to do the thing and be able to leave. I have driven back out of places and never got out of the car if I see cars 3 deep like you will come out and be blocked in until midnight or if there is a line that goes with that confusion.
A small haunt does not support other things outdoors well. People believe they have come and done what they came to do and want to leave.
Another fabulous post from the U.S.Department of Wild Imaginings, now in spectaclar stereo, sponsored by the Adhesives and Sealants Council, suggesting ways to stick things together since the 1800s. Not fabulous in a gay way. Your results may vary. Illinois residents add 8% sales tax. These posts have been made by professional post makers, do not try this type of posting on your own without extensive training, lovely assistants and a trusty clown horn.