The words you're looking for are "I'm making money with a product that has fixed costs and variable income", not passive income. It's a pretty well known model

The words you're looking for are "I'm making money with a product that has fixed costs and variable income", not passive income. It's a pretty well known model used by a number of companies such as Microsoft. You're also selling 'mining picks', so I'd guess your product has a lot of potential.