Micro-Mark sells the IRDOT (Infra Red Detector of Trains) for $22.45 each in lots of 3 or more, which would be half the price you're currently paying.
http://www.micromark.com Catalog item 83232
Are there any inexpensive 4-wire optic sensors that I can use on our N gauge layout for light changes? Say when a train is seen on a track the light goes from green to red for other traffic. The ones our plant electrician purchased are very expensive. A npn 4 wire object sensor but $48 ea.! We are a nonprofit club where our dues pay the bills and we have close to a half a dozen active members. I need to get a dozen more sensors soon as MR is coming out in May to our club. Thanks for any tips! Jim