£283.90 for a set of wheels?
Yep, I'm afraid that the market for this type of vintage wheels is always fairly high. You understand that those are in very good shape, from the early '80s and Kryptonite to boot. Those are in a semi-soft polyurethane used for street carving and skatepark bowl riding.
I've been skateboarding since the early '70s and had my fill of different skateboards, wheels, trucks and the likes. Kryptonite wheels were my fav for a mix of street/skateparks surfaces.
Last time I checked for vintage Sims wheels (in their original package) they were going for more than $240 (example)

You could try to contact Valterra Skateboard to see if they still have the re-issued wheels.
Longboarderlabs.com might have a re-issued Kryptonite yellow original softness for less $$