Very good, and another suggestion...
This is a great game and more addictive than many puzzlers. Here are some suggestions I have on how to improve this for the final version...
-As it is, the in-game instructions are rather confusing. An honest-to-goodness tutorial would be nice, if only because this works a lot differently than most pozzle games.
-Agreed with the last guy that there should be some code in place to ensure that there are always combos. Perhaps the addition of a "wild card" gem which can be combined with anything else would be helpful. Alternatively, you could simply have the game continually check to see if there are available combos and, if not, give you to option of randomizing the board.
-One way to add challenge in higher difficulties is to give customers more complicated demands, such as "Use this AND this stone" or "At least 10 gems long" or "At least 2 combos." Stuff like that.
-It would be nice if you could use the money for something. Perhaps, between "levels," you could buy upgrades like more expensive jewels, longer chains, and other bonuses.
-Building off the above, extending the single-player game into a sort of campeign mode would be cool. It would be separated into "rounds" where you have about 20 appointments each and then between rounds you can buy upgrades for your store with the money you've earned. (Of course, this might be way too much to add.)
So those are my thoughts. It's a great game on its own though. (Like a guy before me said, in beta it's better than many full version puzzlers.) Can't wait for the final version.