Tubes are cheap. It's labor that costs. I'm guessing you've got 12AX7s in the preamp, and they run about $20 new. I don't know what would happen if you run it all the way out, but I would expect "not much." A tube is just a great big transistor that passes current according to an input voltage, so it's not as if you will blow something up or hurt anything on the other side of the amp or input circuits. If it goes all the way out, all it means is that no current will reach the other side. It will essentially be "off" or in standby mode. And since we are talking about the pre-amp tubes, those are something you could replace yourself if you were inclined. They generally don't need biasing, although if you are driving them to crazy levels they might.
I recently bought a Kustom V50 and it is also obnoxiously loud. I don't have to drive the tubes to get it to painful levels, and I'm fortunate that my practice spaces are pretty noise complaint safe. I would like to overdrive it for stages where the amp is running through the PA, though, so I can turn it down and still get that "loud sound." One of the benefits of this amp is that you can re-tube the power side and not have to re-bias anything, so it's something I can do at home on my bench.
You might hold out for time travel or worm-holes to another dimension or something, though. Anything is possible.
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