What's the Cost of Invisalign Replacement Tray?

Amongst several orthodontists I know, the average cost for replacing a single aligner is about $100.  Therefore, a set of aligners will generally run about $200.  You'll have to check with your provider to ask them about their particular cost for another set.

It will depend on the specific office that
you are treated at. Every office will have a different protocol for replacing
aligners. Some require a fee to replace trays and some do not.

Even Invisalign Teen has a limit to how many free trays they will give before they start charging.  Many offices will replace the first lost set but charge after that, usually 100 each (200 per set).
If you feel you are prone to losing them, don't do Invisalign.  Frustration will be felt by everyone.