I have a Brother MFC-9440cn that does great on notes, photos, basically anything flat. It doesn't do well at all on coins that are slabbed or in air-tites or other holders. As far as I can tell there is no way to adjust the focal range. The surface of the holder or whatever is in sharp focus, but the coin inside is not, so I use a camera for those.
Aidan,
These coins were scanned by an Epson V500 photo scanner. Again, it only cost $200. Judge for yourself. They are all in holders which does distort the image a bit.