Good slide scanning service vs. good slide scanner for Do-It-Yourself?

I have a client who wants to get (over time) 2,000-3,000 slides scanned.
Output will be for web, so 4000dpi is not req'd. I need to help him
determine if it's more economical to send them in batches to a lab or invest
in a scanner and do it himself. That leads me to two questions for those of
you who are experienced with such issues:

1. Who is a good scanning service that could to a big job like this
(incrementally, in batches) at a good price?
2. If going with a batch slide scanner, what would be a good unit? (my only
familiarity is with an older Coolscan)

Thanx!
Wm