Dorpers are a minority breed here in UK so scarcity means they will command the prices you quote I think
We used a few rams and they are terrible on their feet (bred in an arid climate, the opposite of Wales)
Think we had 4 rams of which 1 never bred because he couldn't walk at tupping time(had to be shot on farm eventually), the other 3 were culled after 1 season because they also had very bad feet problems
If I have a lame ewe now I can put good money on it being related to one of these rams somehow
Just my experience
They look pretty though with they distinctive black head and have good growth rates but poor shedding ability
There is a Dorper society website----go see some sheep if you want some, if you see a permanent footbath setup you will know why