I bought five Siemens 6922 input tubes from ebay for a total of 75 dollars a year ago. THAT was a great deal. Excellent tubes too, NOS in the box.
I also bought a totally fried EICO amplifier as a parts amp to the EICO that I have that needs some work, and it came with quite lively yet Mullard EL84s and some Sylvania and Mullard 12AU7 and 12AX7s. Paid fifty dollars for the amp and tubes together. Another good deal, that I'll appreciate whenever I have one of these overhauled.
If you look around, you should find some bargains. I honestly think that tube choices are as significant as wiring and footer etc. concerns, and clean power. Even in my EICO when it was up and running, which is far from the minimalist circuit and single-ended design of my Decware Select amp, and not too dissimilar in topology from your amp, rolling tubes made significant differences. And I'd invite you to consider rectifiers in the rolling as they always surprise in the differences they make.