As we all know, Frenchies are an expensive breed to care for!
The stenotic nares surgery itself isn't terribly expensive, but many Frenchies, as well as other brachycephalic breeds have elongated soft palates that must be reduced. The palate surgery can be very expensive, particularly when performed by a board-certified surgeon, and it can be risky. I spent about $2200 last year on nares/soft palate surgery for my Frenchie. In addition, many have sensitive stomachs and suffer from various allergies.
I haven't heard of Puppy Spot before, but it sounds like an online source to buy dogs. It is never recommended to buy a puppy without having the opportunity to view the parents and their environment. You will want to examine the overall condition of the parents, including their temperament, as well as the puppy's. How would one know if the puppy is coming from a puppy mill or similar commercial breeding operation? I hope you are close enough to go in person to get the puppy. Best wishes!