I have a massive stash i've collected over the years so I rarely buy. Generally I will snipe NOS stuff from the forums or reverb though.
If I
have to buy new I will generally do 1. Dougs, 2. Eurotubes, or in a pinch get Mesa str branded tubes from the big stores.
Since I made the switch to (admittedly expensive) NOS tubes, I literally never have to change tubes.
I get it though. The sticker shock for something technically "consumable" sucks. But if you bias and match correctly with them, the old shit is made better and lasts forever.
If you have a "Forever" or #1 that is your main squeeze, I highly recommend shelling out the cash - youll save money in the long run. If you have a stable that is constantly going in and out, constantly buying and selling, then get new tubes from Dougs or Euro.