The correct answer is that Lane nor PSP have any idea what paint will be sold for until it is actually being sold.
The vendors pay PSP for the right to be on site selling paint, but they (vendors) have complete control over their prices and Lane is not privy to their plans until they open the doors of their trucks.
I do know that I have seen paint sold for as low as $20 a case(not very good paint) and as high as $80-90 for top of the line paint like Imperial and Evil.
You are also allowed to bring in your own paint if you would like.
I would suggest buying paint at the event. You can try a little of everything and make decisions on price/quality in real time. Some days this ball shoots better than that one, and a particular run of paint is shooting well. You favorite barnd of XYZ paint may usually shoot fine, but for what ever reason, the particulare batch of ABC paint is shooting like darts today, and that is the run that is being sold off the back of the truck parked right there on the venue grounds.