New Brownstone Lot Line Windows from Marvin for Sale

Hello, We had three lot line windows created from Marvin (double hung, paned glass). But we were not able to put them in because of budget reasons, and when we found out, it was too late to cancel the Marvin order. Does anyone have advice on what to do with them? They are extremely heavy. Is it worth saving for a future owner, donating them to charity, or trying to sell them? They cost about $20,000. They are made to match the look of the original windows on the front of the house.
Thanks.