Well, the budget can get out of hand if not kept in check. You can also get a little crazy with cosmetic crap when getting into keyboards (different key colours, custom keys, skull keys, Ripster keys, whatever).
There's two distinct things with keyboard following, and a lot of these concepts apply to any area of interest. In pretty much any area you look, there's good stuff and there's crap. For a lot of people, keyboards are tools. They aren't just the thingy that let's you type your facebook updates on your crappy appliance-grade computer in the corner of the kitchen. We make our livings typing on keyboards, even if not programmers. Professional mechanics usually buy good tools - not the cheapest thing from the local made-in-China mart. Dentists have very expensive tools. Professional racing drivers pilot cars which are a significant investment. Even non-professionals bother to spend money on good tires for their car.
I've always thought that one should have good peripherals. Peripherals are how we interact with our computer (and all of the applications and people we interact with using it). What's the point in having kick-butt hardware but $5 speakers and a $50 display?
So:
1/ Keyboards are tools, good tools are worth the cost especially if you feed your family using those tools. I don't include cosmetics in this category. One you've started to invest in quality switches and construction, however, something like dye-sub or doubleshot keys upgrade the keycaps to a quality level consistent with the rest of the board.
2/ Even if you don't feed the family with your keyboard, there's high and low quality items in pretty much every category. This is just one that YOU appreciate. Your friends might appreciate wine, shoes, suits, cigars, scotch, TVs, fine German automobiles, audiophile, whatever.... There *is* a difference, and you appreciate it. End of discussion - who cares what they think?
3/ As a primary hobby or a "collection", people can start to drop money on cosmetics. It can get out of hand, and is not understood by the majority of the population as easily as superior functionality is, but if they aren't hurting anyone.... I'm only interested in custom keycaps as a matter of quality (i.e. doubleshots). I would not bother to customize keycaps on a $2 rubber dome keyboard under any circumstances. If I'm in a situation where I'm upgrading to doubleshots or PBT for a functionality reason and then there are sub-choices allowing customization then I'll bite. I'm not looking at my Realforce thinking "what this needs is rainbow keys!". If I could have ordered my Filco with a doubleshot option right from the factory I probably would have and that would be the end of that.