@Flavin913
Yeah, as far as "fair", I think it's safe to say that most Portal players would say absolutely not.
Apparently it's capped by the minute if I remember correctly. Progression on that front is at a snail's pace. Solo and coop are capped as well but do allow Mastery progression along with XP which is presently the only way I can unlock other new weaps, accs, vehicles and additions, etc.
The only thing you can gain in Portal custom is XP. ....but you're right that Official Portal games allow you to progress in other ways too.
I haven't really paid much attention to a lot of it since most of my time is spent with BF3, 1942 and some with BC2 assets which are all unlocked. .....it's just 2042 that is locked and to be quite frank, I really haven't had an itch to create many Experiences using those assets. ....having too much fun with the legacy stuff.