Simply compare it Call of Duty series for example. You pay 60 euros just to have 5 hours of singleplayer and about half a year of MP, which never recieves a major update. Then a DLC comes out and you have to buy it for a lot of money again. Sometimes two or three come out so in the end, you end up paying over 100 euros just to have the core and a couple of updates. And you do this every year because majority of players moves to the newest game when it comes out.
Whats more, iRacing is not really meant for teenagers. Even some of my adult friends are unable to drive iRacing (even slowly), it requires a huge amount of practice in order to be competitive and the hardware required is a bit expensive for youngsters as well. I liek that iRacing is a domain of adults, because they are usually reasonable and car drive as they should (of course, there are exceptions and it's a shame they often behave like that).
iRacing continually develops and you can only buy a content you want. It is possible to play for as low as 50 dollars per year if you're smart enough to use promo actions. Then you can buy content you want. You usually buy a content you want to race, but you have to buy it only once and tracks (which are the most expensive part) are usually shared amongst various series so you are buying a lot.
Yes, if you bought everything in iRacing, it would cost you A LOT. But people often see it as their hobby and buy tracks and cars very slowly as they make progress so it's not expensive at all. And it's not much compared to other multiplayer games as well considering it constantly improves and recieve new and new experience all the time. I would say it's worth IT.