Please correct me if I am wrong but I think price can be manipulated, maybe for short time, but can be. I read about these telegram groups which dictate members what to do during agreed time on market. And you can see very often traders putting absolutly iracional lower and lower offers, even the market has positive growing trend. People are easy manipulated, if they see a lower and lower offers, they usually start cooperate and start putting their offers also lower and lower. Maybe I am already paranoid   but on my marketplace I see now every small grow to 3600 eur, to be pushed back by a huge amount of very low offers, which allways appear from one trader in a seconds (using bot) and you can be sure that in 30min is price back to 3390-3400 eur. I think it is easy to manipulate price down. I can not imagine how to manipulate direction up.
But maybe I am wrong and it is just coincidence. But if such a traders operate on each marketplace....I think it is possible to move the price down.