A tale as old as tiiiiiime..
I was mulling it over and wondering whether people with more expensive hobbies also have these same conversations; motorsport is the main one that comes to mind as something that's not too uncommon but very pricey to be involved in. From what little I know, even the cheapest forms will cost a person a fair bit more than being involved in airsoft and if you get in to really fast cars/bikes and racing them the costs go bonkers. Real firearm competition is probably a bit different in that there aren't that many types of weapons we can own in the UK and a normal person will be legally limited on how many firearms they can own, however the cost of ammo and range fees can be pretty high when you attend the different events.
'Airsoft' is such a blanket term that asking 'how much does it cost?' is literally the same as asking the length in centimetres of any given woven braid of cordage. There are folks who've got 1 or 2 guns, a set of gear sufficient to play and that's it; but they'll regularly travel around the country paying for hotels near to 2-3 day events plus all the extra food and fuel costs and using loads of pyro etc. Then there's the opposite kind of person of course, and there's everything between as well.
Some people have 3-4 amazing PTW/MTW/NGRS, some people have 30+ stock budget line CYMAs. Personally I like gucci kit (clothing and LBE) and furniture for RIFs, but I currently draw the line at high end real optics like EoTechs and ACOGs. I could elaborate on my thought process as to why, but there are a few airsofters out there who love those types of optics and own a few of them, highlighting the fact that what makes sense within your own personal lump of grey matter won't make any sense within the grey matter of many other people. Long as you make peace with the fact people like different things and then actually act as such then it's all gravy.