I have a Canoscan 8400f, that I bought for about 150.00 two years ago. It has an adapter for four slides at a time.
The real key to scanning is this: Are you scanning for printing to hard copy, or are you scanning for a video disc.
If you are scanning for printing, it will take a considerable amount of time to do this, as you have to scan at a very good resolution.
For video (TV) display, you can get by with much lower resolution scans, and this makes scanning a lot faster.