To help prevent pricing mistakes without questioning the price itself, please require a period or decimal point when listing any item for sale. This would prevent mistakes where the seller types "80" in the price box thinking it means $0.80 while the system interprets it as $80.00. In this case, a pop-up could show simply reminding the seller to insert the decimal in the proper place. The pop-up does not question the amount of the price. It simply asks for proper formatting.
Comments
I'd even go so far as to request leading or trailing zeroes. So 0.80 or 80.0 are valid but .80 or 80. are not.