the questions remain":
" How is it possible in a so called decentralized market, where the exchangers are(should be) independent entities, ALL of them to have the same price when they certainly don't have a "the same" order book(same clients, same orders) ? How is that come? "
I saw many example when the chinesse exchangers dropped or raised the price and all the exchangers did the same without any valid justification. Their orderbook was the same.
The price is artificially created not by users but the exchangers according to their interests.
Probably, but let me post a simple example, if you see two, three taxis,etc on your way parked waiting for your chords, you give a look first to see which you decide, based on state of the unit, driver, price, etc...
next; you already carry an expected rate than they can overcharge you, so if any of them wants to charge more than you expect you'd go to the next just to see if you find comfortable according to what you expect to pay, somehow taxi drivers have to undergo even set price otherwise they will lose customers. I guess a similar thing could happens in the exchanges.