I almost agree, but...
2. No, the best moneymaker is a sonic cleaner so you don't have to take the gun apart but you can charge the same as if you did.
3. The "box o'gun" ALWAYS has broken or missing parts, which you are expected to replace at no charge as part of putting the junker (they are always junkers) together. If you charge a reasonable amount for your time, the customer tells you the junker isn't worth it and to keep it, then walks out without paying.