I think a lot of it has to do with expectations. I had low expectations, that were exceeded. Had I bought a frame from a name manufacturer in this country then I would expect an awful lot more, as I would have paid a lot more with the expectation of greater come-back should something go wrong.
PX will do you a carbon frame for £250
I did look at them at the time I bought the frame and their cheapest frames started at £500, prices have fallen a lot in the last year.
I paid about £350 all in for the HongFu frame. There would not be the same economic argument to buy from China now.