I had the work done because I'd planned for a head rebuild, and was offered a deal on the cams & pistons.
The verniers were a bit more challenging, as it turns out STM have stopped making them to focus on slipper clutches, but got some from the US for £299 inc Vat.
The work was done at MotoRapido in Winchester, and was added into the cost of a 12K service and Top End upgrade so, you're looking at around £750 plus parts and vat for the basic fitting of the cams etc, then dialling the cams in takes a little longer so you're looking at a few hours labour there, and add on that a bunch of dyno runs for setup of the chip (I had 14 runs), so more labour there depending on how precise you want to be.
Used is fine for these parts, as long as it's a reliable source, bearing in mind cams can be scored by bad rockers, pistons can be in all sorts of a mess etc...
To be honest, I'd check with Harv to see if he's had the head rebuilt already, if he has then I wouldn't go to the expense for the sake of it. The only reason I did this is because a head rebuild was being done anyway (had to replace all the rockers too / thank christ for ebay and a set of low mileage heads.) so most of the labour was being absorbed by that. If you don't need a head rebuild, 853's about the same cost, and will give a similar power gain.
If you're thinking of this, you'd be looking at between £1.5-2K, although you end up with a bike that punts out more power and, is effectively an SPS in a bip frame.
Performance wise, I'm really pleased with it, last couple of weekends have seen me upsetting Blade and GSXR owners, especially when they double take the 748 logo's
and I'm not a gifted rider, leaving a safety margin the size of yorkshire when on the road.
Next I'll be working on my skills, 3 TD's booked already this year, nad trying to juggle work dates for a return to CSS, although I'm trying to convince Wilf at MotoRapido to let me take his 853RS out. Just to see where to go next......Although he's got to rebuild the thing first.