Actually the card number is stable, but unique to the iOS device. (It uses a Device Account Number in place of your Primary Account Number, with a different DAN for each iOS device you use.) The part that changes on a per-transaction basis is the security code (similar to the CVV2 number printed on the back of a physical credit card).
But yes, I wish everyone supported Apple Pay. It’s by far the most secure way to pay with a credit card at the moment. It should be pretty easy for Glowforge to add support for it, assuming their credit card processor supports it. From what I’ve seen of the Apple Pay documentation it looks very straightforward.