Bagster do 3 products.
Seat covers - they send them to you, you fit them.
Comfort Seat - you send them your seats they repad and recover them - takes 6 weeks (so you need spare seats)
Seatster - Complete seat unit - new seat pan, foam etc - 6 week delivery but you still have your seats, not available for all bikes.
Mine cost £320 - but IS a big improvement comfort wise.
I have a spare Z750 front seat from where I was trying to get a set to send away to get a comfort seat (before they announced the 07/08 Z750 Seatster) which I am going to send to this guy to get done
http://www.diggerseats.co.uk/ - I got a quote that was about £60 with a few days turn around.......