If these birds are worth their money, where have you showing them and what have they won. Just because they came from, what you say, is a good loft doesnt make them good pigeons.
I know what most fanciers regard as leading authorities in gbh's and none of them leave next to near the channel islands, in fact a friend of mine won the npa show with a gbh so i know what im talking about.
This car compaision you are using is ridiculous, a car is nothing in comparision to a pigeon, with a pigeon its down to morale what you sell the pigeon for.
I know the market sells the birds for the prices you have given and I think the market is overpriced. Just cause others sell them for this doesnt mean you have to, I was always reminded in school that "if others jumped of a cliff...etc"
Believe me i could afford it, if I wanted to get gbh's I would go to someone who is winning shows, not a racing man who thinks he has struck gold.