I have a question and I hope someone will answer me. Can I change the price of a tank, soldier or plane on the map through the scripts?

I don't think that's possible. Even if you want to change a unit's cost through map.ini that would be very bothersome and limiting, as you can only use another unit's build cost and replace all of its code with your unit's code.
I'm not sure about units that do not have their costs specified in their main ini.big files, e.g. system units or weapon objects.
If you change the buildcost through map.ini, it will only change the visible number in game but will still deduct the previous cost from your money.
Buildcost in .ini 

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Heyo, it's actually possible to change.

Use this:

PlayerTemplate
ProductionCostChange =