What is the crossover point ?

By dividing one into the other(Net Worth/Money Spent); you will, sometimes, find ones Love-for-Music quotient. More often; others Love-for-Equipment, or I-Have-it/You Don't constants must be factored in. There are too many variables(diverse degrees of those constants) to offer a firm answer to your question, however.

Different formula:

When Cost of System>Cost of Car, a line has been crossed. When Cost of System approaches/exceeds Cost of House, intervention is required.

It would be the same as for any hobby. What percentage of your disposable income are you willing to spend on your pleasure rather than your needs or savings. Once you exceed that amount, you are certifiable