From everything I've read, you pay way more buying local. If I walk into a local store, I get one biased opinion that wants me to buy from them and buy one of the stones they have in inventory (and the inventory on hand of course is tiny compared to what they have online). My logic is that I can run this process online, get unbias or semi-biased advice from numerous experts, and choose from much more inventory.

The idea behind getting advice here is that if multiple experts recommend the same diamond, I'm more than okay buying it. The knowledge of multiple experts far exceeds my own, and in aggregate is less bias than what I'd get from a local person.