Two points
First of all I believe that assets, even if they’re re-used in many games, do not always lose value through re-use.
Some might, but others may even gain in value as they become accepted as a standard. UI is an example. Look at your average MMO skill icon, the questionmark for quests, map icons etc.
If used correctly, by that I think of correct placement into a unique level for instance, one single asset could be re-used hundreds of times and you won’t even notice it’s the same because it’s either just a part of the big picture or fakes the mind into believing that.
Think of trees, flowers, stones, junk on the ground etc. Things that make a setting feel complete but nobody ever really looks at if you design your levels correctly.
Of course you should always present the player with unique assets as well, to differentiate from other titles.
My second point is that assets do not define the average game (game meaning: creating a setting/environment that follows certain rules and allows the “player” to interact with these in a risk-free way).
You could create 1000 RTS games that all look different but have exactly the same mechanics and nobody will ever bother playing all of them. Not even a fraction. Why? Think of what games are and you’ll quickly find out.
The problem isn’t the price of assets - the problem is the lack of really innovative ideas and finding out (as a developer) what the core mechanic really is that is enjoyed by your audience.
A great recent example is Trine 3 - which was impacted a lot by the fact that they focused a new gameplay combined with a very expensive asset pipeline in comparison to earlier titles. The result: the core audience never cared about their new gameplay / asset quality and as a result the sales are poor. I’d even go so far as to bet that if they had just re-used all of their older assets (re-worked slightly maybe) but improved their core gameplay mechanics and created a new story it’d have sold a lot better.
So in closing I have to admit prices aren’t so low that average hobbyists will just go through the store and buy everything - but they should be able to sandbox enough to refine their gameplay, script and all that and decide what asset quality they need to finalize their game idea. And in that regard the prices of the assets on the store are perfectly fine. Especially if you look at the license (which I believe is totally for small hobbyist teams)
The only negative point I’d have to make is art asset consistency. Currently it’s not yet perfectly viable to just buy certain asset packs and expect them to harmonize well together. For that the number of available assets is still too low and the techniques / art styles used to create them differs too much.