A lot of these "online" vendors are actual B+M stores also (GOG, Dscaasi, etc), so you can see diamonds or talk to the jeweler face to face if you need to. If the savings of $1K and taxes on top of that is not worth it because you can''t see and touch the items you want to buy, why not take that money and take a little vacation to where these stores are. So, you get a nice weekend vacation in a nice city, still get the same online price, and still save on taxes because you can have your ring shipped back to your home. All while coming in at probably the same price as more traditional B+M stores by you. You just have to do a little of bit of work in advance, like narrowing down diamond choices/setings to a few so you can decide. You can also have an appraiser lined up at these cities and have them appraised the diamond before making the commitment to buy. So, with a little planning, you could resolve all the uncertainties. Just a thought. Good luck on your search.
Jim
Jim