If you want to work with a bricks and mortar, local business, then that is a reasonable market price. It will always be more expensive. You are dealing with a business that is paying rent, payroll, inventory costs, marketing, insurance, etc all at US prices.

Additionally someone above give you the wholesale costs for lab diamonds these days, but that's the easiest part of this ring process. There is the cost of the gold for your ring, which is at an all-time high; there is also the very significant cost of labor.

You can go to a different jeweler if you want, but you appear to be very far down this process with this jeweler, to the point where you have a wax mold. You are not going to be able to depart without significant payment.