Well, you havent gotten much feedback. Sounds like a great idea. Pricing isnt to high, except for the paint. $20 for 500 rounds??? Learn from the successful fields and buy/sell by the case. You can break them open and then sell by half a case (1000 rounds) for a slight mark up.
One thing about tactical paintball: the bigger the better. Do you by chance play Paintball at all. Or even just playing tactical shooters like Modern Warfare? If so, that will be a big plus. Players can almost always tell if the field was designed by a non-player. You have to think tactically for a tactical field. See angles, see points that offer an advantage and such. If you dont have any idea what im tlking about, see if you could find some ex military (or current military) guys or even cops to give you advice for design. If you design it wrong, we wont wanna play there as much.
Again, as low as you can possibly make the prices, do it. Paintball is expensive, and the cheapest field is the one everyone goes to for weekend fun. You only go to the nice fields when you got a new paycheck, tax returns or a bonus. I generally go w/ a friend and split a case of paint, so my daily cost is about 40-50 (entry, paint and gas, plus drinks). One way to make money: SELL DRINKS AND PIZZA! Playing makes you THIRSTY, and nothing goes better with a coke and sore feet than pizza.
Finally, dont forget about a crucial part of paintball. Propellant. Since i dont think you play, here is a rundown.
-CO2- Most enrty level guns and players use this, and it is great for long day games/ scenario as you can get alot of shots out of a 20 oz tank.
-HPA/N2-Higher end guns use HPA, or High Pressure Air, which is basically the same as Nitrogen (N2). This comes in two forms, 3000psi and 4500psi. 3000psi can be found in a scuba tank and is relitivly cheap, where as 4500psi is most often used for high level competitions and less commonly used in scenario ball. They are both the same stuff, and both can be provided with a compressor.
CO2 generally retails for about $5 for 20 oz, but can be upwards of $8. HPA ranges anywhere from $8 to FREE! Get a compressor and make it free, then advertise free HPA, and you will bring in more experianced players (or players w/ rich parents, either one). Dont make gas expensive, cause like i said, paintball is already too expensive.
Best bet is to make you money on the paint. Its what everyone else does and they stay in business. Dont go above 15-20 for admission. Any more and you risk loosing players.
Hope this helps
-PS- where are you building this (state?)