I haven't been to any sales this year - in fact I'm not sure if there have been any sales yet this year - but if I was buying privately I'd probably expect to pay £40ish. Maybe a little more if they have superb fleeces, interesting colours, etc. Up to £50 for the shearlings if so.
I wish they should be more, I think Shetlands are wonderful sheep, but good registered ones mostly haven't been fetching a lot more than that in recent years.
Some of the rarer primitives fetch more because they are harder to come by.