We (historical society) purchased an Epson v750 scanner a few years ago for about $800 (grant money). It scans all/most photographic medium – slides, negatives including glass plates and lantern slides, film and prints. There are holders for the formats of various sizes so you can scan multiples at one time if you wish. There are options to store the target image in almost any format and resolution. We’ve been extremely happy with it. The light comes from top and bottom with a plate that covers up the top light for standard scanning. The only downside which has not affected us at all is that the webcam on your computer has to be disabled in order for it to work. I don’t know the cost of companies that scan slides, but I would guess it could add up for large quantities.