Actually Cornford use tag board, which is often wrongly callled PTP. True PTP means that the components are wired directly to the valve sockets etc with minimal tags. Very few amps are truely PTP and making anything more than a simple amp using PTP is very hard. Contrary to popular wisdom repairing PTP amps can be a total nightmare — a well laid out PCB is much easier to work on. Incidentally I don't like tag board construction much either — eyelet or turret board is much easier to work on. Additionally the material used to make tag board, synthetic resin bonded paper, is a poor material for the job as it can absorb moisture and be prone to DC leakage. I have experienced this in amp I've built in the past and no longer use it.
I don't think Cornford's prices are out of line with what you should expect to pay for a hand-wired amp built in the UK. It's labour intensive, requires a lot of skill and you have to pay a proper wage, not a Third World wage. Regardless as I have posted elsewhere, I would agree that Cornford have made a big selling point of the fact their amps contain no PCBs to demonstrate that they are superior to other amps....
Regarding "limited-use amps" — well most of the working, ie professional, musicians I know (and have done work for) use "limited-use amps". Their limited use is in fact their strong point. You can get to a gig, plug in and there's you sound. If you don't like the sound of the amp, you've got the wrong amp. These amps sell on the quality of their sound, not the number of features.