I think the site is great but in terms of paying for features I would say "maybe." Only because it would depend on price and what the features were.

I have one suggestion though: Why not charge a minimal fee for uploading ads? Not like WTB ads or small ads, but if your ad is >$10 you could add just a $1 charge and only if the ad sells. It is a small amount that I don't think people would be averse to, certainly not when it only gets deducted if the ad sells and when you get the kind of market access / free exposure that the site provides. I think it would provide a lot of revenue with minimal inconvenience.

And you could make it value-added by allowing bigger picture upload for those ads etc. which would increase sales I am sure.

I think allowing people to have more server storage for PMs and more image storage space, as Max suggested, would definitely entice 'razor porn' posters and people who do a lot of sales from the site through PM to become contributing members.

I think I would definitely join if I started selling stuff if the PMs + images / server storage were a benefit. I'm not sure that a blog and e-mail opp would really sell me - I have like 3 e-mails and don't blog; although I could definitely see some of the restorers etc. blogging their work which would be a real asset to the community and drum up business for them (if they want), which is good for everyone.