Its interesting that the conversation went the way of tube costs. I saw @ProfFalkin post this and, reflexively, I almost signed up for it. Then I thought about the 300B costs…
Not to off topic things too much but I think that is the genius of Donald North coming up with the Starlett, that things sounds good stock and if you want to roll its pretty cheap. I bought all kinds of NOS tubes just for kicks and spent around $200 - whats a NOS 300B cost? My current favourite tube complement in it is a total of $50.
Not saying that the Starlett is better than whatever 300B you want to compare it to but I think it may be a steal at current pricing. The only potentially crazy expensive tube on it could be the 5AR4 which can run you to just around 1k depending upon what you are after. I got a NOS Mullard coming that will be the most expensive tube I will try with it but even that wasnt break the bank.
Ive even noticed prices going up in the last month on certain tubes, its getting to the point that people are going to have to design amps that use more common tubes (hopeful), companies are going to have to make better new production tubes (doubtful) as really good tube amps are going to be out of the reach of even audiophiles who have some financial means behind them.
So as @M17XR2B stated correctly, the true cost of a tube amp is hidden in the nebulous nature of the tube market. Gives me great pause when considering an eventual upgrade, you almost feel like you should buy tubes now for an amp you may never actually buy! Crazy stuff.