Beware of backyard operators offering low prices. These low prices look great until you start to compare the differences.
Firstly the resolution is often very low. We generally scan slides at greater than 2600 x 1700 pixels after cropping the uneven edges (can be enlarged to an A4 print). This means that we provide more than 4 x the resolution of a 1200 x 800 pixel scan (a 1200 x 800 pixel scan equates to about 10cm x 6cm at photographic quality).
Furthermore, many operators only scan the slides using the scanner's inbuilt mould removal and colour correction capability. This is only half the job. The slide then needs to be manually edited in order to get the best out of it. This is where faded colour can be restored further, excessive mould can be further removed, etc to bring out the best of each and every image.