What are we going to do to keep the gangs of well dressed men from robbing the parking lot? How will they be able to tell which well dressed men are there to rob them and which are just there to be robbed?
"A bad day at Disneyland is better then a great day at work." ~ Max Fischer
Each booth should have a set-up so if the cashier hits a button, a can of BRIGHT spray paint tags the car so PD can catch them. Or, if they really wanted to spend some money, they could shoot a GPS tracking blob onto the car and just follow it via computer.
Our local PD just bought that set-up to help prevent car chases. Certain patrol vehicles are armed with it. They just get behind the bad guy, hit a button, and a glob shoots out 50ft. and sticks to the car, often without the suspects knowing. Then, they just back off and let the computer do it's thing.
Another cheap solution is to give each cashier a 'dye-pak' its a wad of money that will explode in bright dye, staining everything.
Also, I'm betting the amount wasn't as small as we are being told. Each robbery took place in the afternoon, after how many cars paid?