Also, tube amps cost more because the components to build them cost more, period.
Solid state silicon micorchips and their related circuits are generally low-power, low-heat, and fairly cheap as the same parts could be used in other modern electronic equipment.
In comparison, tube amp parts are larger, higher power, higher heat, and not real common in much anything else these days except the random boutique hi-fi sound systems.
But with stuff being made in China now you can get an all tube amp for less than $100 (Epiphone Valve Jr.)...or you could spend $2600 on a Bad Cat made in America.
The difference, imho, is huge but still, it's just to point out that tube amps are not as expensive as they used to be and some are much less than others.
Even though I use a modeling amp at church, the amp I reach for when I do studio work is either of my tube amps.
They just sound "better".