I've had delks since the late 1980's [converted optonics B4 that, which I still have !!!] and have NEVER had a problem with them, they are 100% reliable, never heard of anyone having a problem with them either, now onto the TXi's with the remote RXi receiver - OK they ARE expensive, but my reckoning is that apart from the hook and the line, the alarm is the next most important bit of kit, and if you do a lot of overnighters as I do, then they're worth every penny
I've seen the cheaper models EV, they're called, they seem to have all the functions that you would need and look to be competitively priced to compare with the Fox alarms - anyone seen the Fox EOS alarms? can't see them standing up to much wear....but I could be wrong...