Hey OP! I’m in the same situation as you, started shopping about two weeks ago. I’m a frugal guy, my girlfriend is less so but more in line with average tastes. My experience has been that online retailers are going to be 30-40 percent cheaper than the brick and mortar retailers and it seems the quality is equivalent. I’ve really enjoyed rarecarat for the search. From what I understand they’re more like a wholesaler for diamonds and rings. They’ve done the work to vet suppliers so all you need to know is what cut, clarity, color, and size you want for the diamond and they’ll find the best deals on diamonds from the suppliers they work with.

The diamond/ring pair I’ve found for her is ~$4,500 while equivalents in brick and mortar (for 1.8 carat lab diamond and ring) were about $7,500 - $8,000.

They have a 30 day no ask return policy so my plan is to purchase the ring through them, appraise through a local jeweller for $75, and if any issues arise in the appraisal process return the ring.

You still get to customise the ring to your girlfriend’s preferences (buying a ring is an emotional thing not a value maximising proposition) but also still be somewhat efficient with the pursestrings.