Based on your assumptions, no one will buy it at all when it starts. But obviously you're wrong.
If it starts at 1 mil coins, why would someone buy it ? It is just an investment. You can risk your money to earn double. It is fair to me even if I lose and also fair to the one that will buy it from me.
Untrue.
If the price is low and there is a very high probability (a.k.a guarantee) that a dude #3 will buy dude #2's lot who bought yours, then why not. Dude #2 is happy to buy your lot because someone is willing to buy his.
This scheme is highly profitable up to two steps forward. Let me explain that to you.
I'm dude #1 and own the lot.
Dude #2 considers my lot. He obviously looks for profit, and thus needs the assurance that someone will buy the lot from him/her.
Dude #2 will only buy if the price is low enough so that another dude #3 thinks he has a chance to profit. Otherwise, he has no reason to buy the lot.
In your case,
You own the lot. It costs 7.5M.
Dude #2 considers to buy the lot. To profit, he would need the assurance of someone buying it off from him @ 15M.
For this to happen, it requires him to think that another dude #3 is crazy enough to think he could sell it @ 32M.
Otherwise, dude #2 would never buy.
In other cases, say under 500K, then it could still work. In your case you just lost your coins