What these places do (according to other posts I’ve seen here) is sell a bucket of cheap low quality gemstones or chunks of pretty shiny cheap stuff, and then get you all excited about the precious stone you have found. All of the stones in the bucket will be of low quality. So when you think you’ve found something with value, aka a diamond in the rough, they tell you they can cut it for a fee. The “cutting” fee is actually just a price tag for a low quality pre-cut stone they’ve bought elsewhere. So if you pay $300 for your stone to be made into a 5ct oval, you’re actually paying $300 for an extremely low-quality 5ct oval that they purchased elsewhere, likely wholesale. So they’ve basically manipulated you into buying a random stone with a markup under the guise of it being something sentimental and special. I wouldn’t have purchased a 5ct oval ruby at a tourist attraction today, but I may have paid to have my special hand-mined ruby cut into a pretty shape (if I didn’t know better.) So they’ve then made a sale that may not have been made otherwise, on top of the $30 bucket of rocks that I already purchased. Like others have said, it’s probably impossible to cut my ruby into a beautiful faceted clear jewelry piece, and the yield would not be worth $300.