We'll for one it all depends on how bad they are. Are the drums, cylinders and hardware good? For some reason trailer brakes parts are expensive. I had the same situation and decided screw it and replaced the whole axle complete with discs, actuator, wiring and misc goodies myself for $850. Still sounds kinda high for drum bakes though.
I just had a problem with my trailer brakes. I took it in and they did a full inspection and bearing repack on all 4 hubs ($200). They then changed the brake assembles including everything from backing plate forward ($300). So I would say $800 for just brakes is way high.
Its not that far off w/labor actually since that is the entire brake system, but for that kind of money you are much better off going to a disc setup. If you look into the link that Troy posted you can purchase a disc conversion kit for ~$400 and a new coupler runs ~#100. With shipping you are still cheaper and end up with a better brake system. If you have a spare day and a few tools it's a pretty simple swap.
Thanks a ton for the input. Normally I would be doing the disk brake conversion but my daughter is 6 weeks old so the wife wouldn't be too thrilled with me spending a day in the driveway when I could be swadling, shushing, swaying and two other S's that I can't remember to try and get the baby to sleep. (the dad's will think this is funny, the guys that aren't dad's yet... be afraid)
My little bundle of no sleep.
I wonder how much it will be to get them to switch to disk brakes? Thanks again.