what do you mean exactly by be aware of, galin?
no harm in paying the entry fee, it's a crap variety of cars & tracks, but enough for you to get in a race & get a feel for the physics & systems in place. if you're curious, maybe plop down on a car you can compare directly to AC, or go full bore & get a 6-pack for the 20% discount (which, assuming you'll use the other content, is essentially equivalent to a free car).
after a few 6-pack purchases i'm only a little over 1 purchase away from all the content i 'want' (& basically need) as a road racer already. it is a lot of money all told, but ive not spent any more than i wouldve spent on random steam purchases for a bunch of games that, for the most part, i quite likely would not enjoy as much as hoped, if even play. otoh with iracing i know pretty much precisely what i'm getting, & its all stuff that will be updated every quarter (? i think) on top of that.*
*unless of course it all goes under ;D