What is the most expensive hobby you have ever tackled?

I taught myself how to be an amateur lapidary, and also learned how to make miniature sculptures out of the quartz I found. Sintered diamond bits for a dremel moto tool are expensive, and sterling silver is very expensive, too, when you're buying it for jewelry making. Also, I was receiving the Rio Grande catalog, and I wanted everything in there. They had tools that make me dream of new and better things I could do...I wanted it all...😂