there is yet one more option to reduce costs, more particular the costs of the transponder.
You could buy the AMB-decoder an loop ... and they buy some MRT-transponders in stead of the AMB-transponders.
MRT-transponders do not have a battery inside but a wire that should be hooked up (as an AMB-personal transponder does) on the receiver.
Advantage of this is that they last much longer then AMB-transponders that lose battery-cpacity after some years.
Other advantage is that your system will be fully compatible with all people that allready use AMB-transponders.
MRT-transponders are much cheaper about 50% of an AMB-transponder) AND you get a reduction if you buy more then 10 (more info:
www.rclaps.com)
... But offcourse the cost of an AMB-decoder is rather high.
Cheapest solution will offcourse stay the I-laps system.
I have some experience myself with Laps Free, that free lapcounting-software and it's actually pretty good.
And you are right that good customer-service is VERY important, so more points for I-laps.