I have a couple of the MTH PRR signal bridges. I just think they look so cool...
I brought a bunch of AC 12v relays from Mouser and the relay sockets, that puts you at about $17 per relay. Early on I used 4amp rectifiers to convert the AC to DC but it was such a pain to solder up everything when wiring up the relays. So I went with the sockets and changed over the rest of the signaling relays to 12v AC. All you hear are the relays closing, a click and that is it. I put them in over 5 years ago. The contacts on the relays are rated for over 1 million uses....
Marty