the coins

I want to open a discussion about the existence of coins - as I see on the market nobody has coins now - or very few still have it.
As I see it, for upgrades on marble, stable, hardwood sawmills and I'm sure that many more buildings it is required to pay 100 coins/building. This money exits from the economy. The coins that enters the economy are from lvl up (100/level) and from the gold factories that are so expensive that you cannot build without first upgrading hw sawmills and marble to the max levels - with coins.
This means that soon there will be no coins in the market.
Maybe I don't see all, please correct/complete me.

There's already a thread for that. Read more here.

I don't say this as a strategy point of view, I think that economically coins are disappearing from the market and the game globally will become unplayable. Maybe you have some folks that can do the math and prove me wrong. If they did that already is ok - we can play on.