How much should I charge?

I have a list of about 60 PR 8 & 9 do-follow sites that allow visible links and are proven to stick. I already offer a backlink service that does 50 PR 4-8 forums but since these are all high PR I was thinking of doing a special offer. I'd only sell 10 packages and I'd guarantee that the links would stick for 30 days or I'd replace them with either double the number of PR7 links or a refund.

For those who pay for backlinking services, how much would you pay for a bunch of links from only PR8-9? (there would probably be about 100)

I'd appreciate any feedback because I want to get as much as possible (obviously) but I don't want to screw anyone over.

Thanks!

Yes. if the links are from urls that have lesser pr, then the price will be significantly lower than they are from home page.
home page you may consider charging on a monthly rental basis.