I've been asking this question a number of times because I've seen a lot of collectors spending huge amount of money buying stuff for their collection, and what do we get out of it? Satisfaction...of course! Indeed, there's no price tag to happiness. Your passion could be in gardening, home decor, sports, books or music. I myself is hooked into gardening and home decorating, but the question, how much I am willing to spend for this depends on whether it would be beneficial in the end?
For example, in the case of gardening, I believed that if I am able to tend a beautiful garden at home, I would be less interested going out of the house coz my home would already be a beautiful sanctuary and a perfect place for me to relax and unwind. That translates to saving money that I am supposed to spend elsewhere every time I get out of the house. Apart from that, if I go for vegetable gardening, I would be saving an extra amount for my grocery budget especially that vegetables can be too expensive at times. I guess others would be spending much for their passion because they are thinking that one day, that passion could be an opportunity to earn. Musicians for example would be willing to spend for special guitars like evh wolfgang thinking that someday they could turn their passion into a profession where they could make it a source of living. I know some people who wouldn't think the same way, what is important to them is self satisfaction. As I've said, there's no price tag to happiness.
How much you are willing to spend on your passion depends on your financial standing of course. I think everyone should consider their priorities. In the end, we couldn't be happier knowing that we are not providing well for our family's needs.