Because the quality is astounding, and because Mesa can say they invented the modern high gain amp (which they did, with the Mark IV). Its just like why are Gibson guitars so expensive! I was blown away by the stiletto, recto gain but with more warmth, and a great clean channel.

Is the boss Katana good for metal?

The Boss Katana is a solid state modelling amp – the sounds are based on other amplifiers. The Katana has five amp models – two of which are ideal for metal, depending on how much gain you want.

Can PCB amps be repaired?

PCBs are hard to repair: A tube amp is meant to be repaired--it not a disposable piece of equipment. If you want an amp that will last a while get one that is hand-wired. PCB construction is usually done save labor and cost so manufacturers rarely use high quality boards or consider the serviceability of the amp.