I'm not clear from what you said whether or not they placed an order with their distributer. The following only applies if they actually placed the order, and you decide not to buy the blades from them:
I'm not a lawyer, but it seems to me that an oral or written contract is still a contract, even if they don't have your credit card, and you may have an ethical obligation as well. I don't see that their skill level, or the time, within reasonable bounds, that it takes the order to arrive, are relevant. You didn't say anything that indicates that they acted dishonestly or unethically.
At least tell the original shop that you don't want the blades, and that they should cancel the order, as soon as possible.
They may be out the cost of the blades, if they can't cancel the order in times. Blades come in many models and sizes, so it may be months or years before they can sell the blades to someone else, or they may take a loss, one way or another. If it is too late for them to cancel the order, you have to search your own conscience for what your obligations are.
Regardless, if they take any loss, or it takes a long time to sell the blades to someone else, it could affect their willingness to do future business with you, or to be helpful to you.
- Just my personal take