I'd not expect to pay more than shearing costs for Herdwick and even at that it would be expensive for what it is. It is a very, very coarse wool and has limited uses.
I was given five Herdwick fleeces a few years ago. It spins into pan scrubber if you try to spin it into anything less than an aran yarn so I got out my big Country Spinner, literally threw the fleece into it in handfuls and ended up with what you could politely call a textured chunky singles yarn. Still a bit brillo like but it made a lovely rug just woven as singles, it was very hard wearing and it doubles as a foot exfoliator.
I was very selective as to what I used from the five huge fleeces though, I only used the best bits and the rest ended up in the compost bins.
I can't quite see myself knitting with Herdie yarn, I can't think what I'd want to make. Slippers? Cat bed? There are nicer types of wool like Texel that wouldn't cost more per fleece usually but would be far pleasanter to work with.