"But firstly I should finish core game. I have a deadline to 10 of December to make version 1.0
1.0 is 10 levels. 40-50 guild-mission"
Sounds good. More missions would allow more time for price mechanism to adjust prices.
"I think I can change price each battle. But also I will make sure that there are victories in different locations and modes, so that the player cannot lower prices with the help of a particular easy mission.
So if player won several times in a row one level I will not lower prices."
I see problems with such approach.
Firstly, there will be no way to lower prices once player won all missions.
Secondly, if you will punish winning several times in row, then players will easily bypass it by letting enemy kill them after each victory. And if you will use limit like "If you won 3 times, no matter if in row or not, then prices won't be lowered next time", then it would be bad too, because isolated number of wins isn't indicator of difficulty. Maybe a player was able to win this specific mission 3 times (NOT in row), but was able to win other missions 10 times (NOT in row) or even more. Compared with number of wins of other missions, this mission probably is more difficult.