There is no tax requirement that you try to maximize your profit or minimize your loss, so if you can sell it for $100, you would report that. You could even destroy it and mark it as destroyed with zero dollars raised.
Depending on how the business is set up, there might be tax value in donating the inventory to charity. The value of the donation would be the cost basis, or the fair market value on the day of the donation, whichever is lower. Because you are having such a hard time selling the inventory at an 80% markdown, you might have trouble claiming much for the FMV of the donation. I don't know if would be better for you to claim a loss on schedule C or a donation on schedule A.
