It's probably just a move towards them requiring more silver thingies as upkeep. Before you'd just buy the plane, and the very occasional engine or whatever. Now you've got to buy ammo every now and then, and all these little unlockables. Apparently they reduced plane prices by 30% (someone here said so, I think?), but in the long run we're still loosing out
Currently if you haven't noticed the parts are super cheap. Also not having them makes the repair prices cheaper. I have yet to see a plane where I had to spend more on upgrades then what it used to cost full price. (Maybe that will happen at the higher levels, but it hasn't up to rank 5)
The non-default ammo used to cost money to reload as well and I don't think price changed; its just much clearer on how much you are spending. The default ammo is still free.
Also, the new 'buy parts for your planes' system feels like either an excuse to nerf everyone or a way to try and hide some planes getting nerfed without people noticing and bitching about it.
The maxed stats are currently what appear if you go to buy a plane on the research tree (that you don't own, if you own it the tool-tip shows what your plane is currently at). In a way I guess they nerfed all the planes to make them feel used, but besides the noted changes you can upgrade your plane to exactly where it was before the changes.
The silver lions cost on upgrades I'm pretty sure is never going to hold you back. The per plane experience requirement will be what slows it down. And that's where the golden eagles come in cause you can skip the experience requirements to get them. I've never kept one plane long enough to unlock everything; if I did it would take a while... A lot of people will pay those for a plane they really like. Which I'm ok with; its a free to play game and they have to make money somehow.
Anyway; having a ball playing this game with a ton of people from DFC. Also if you haven't tried the co-op campaigns or historical missions they are pretty fun with some friends.