I suppose "expensive" is relative to the individual, but I see nothing wrong with a person who loves a particular activity spending as much as they can afford to maximise their enjoyment, as long as it doesn't drive them into debt or mean that the family goes without.
I have reached the age where I am comfortably off and could buy anything I want (within reason - I couldn't afford to buy a 100 foot yacht - not that I want one, I don't get a great deal of pleasure out of possessions, plus I get seasick), but I find it difficult to get over the way I was brought up - in a low income family, where money could not be wasted, and I still have a bit of a guilt complex about spending extravagantly.
I have three bikes at the moment - all made up from new or nearly new frames and components bought after searches of ebay or car-boot (or yard) sales and I love riding each one of them. The mtb and the hybrid cost me about £150 each, while the road bike cost me a staggering £400 (although it would cost £1200 to buy new), but I get a huge enjoyment out of making up my own bikes, and changing the components when I fancy upgrading.
I have a husband & wife pair of friends who pay thousands of pounds for their carbon bikes with electronic gears and they absolutely love them, and great for them. I know they get huge enjoyment for their money, but so do I, and, at the opposite ends of the scale those choices are right for the both of us.