Your profit (at 0 unit cost) will be (Sales not refunded * 0.7-refunds * 0.3) * price If Sales not refunded/refunds<0.3/0.7 ~ 43% Then profit can be negativ

Your profit (at 0 unit cost) will be (Sales not refunded * 0.7-refunds * 0.3) * price If Sales not refunded/refunds<0.3/0.7 ~ 43% Then profit can be negative (you lose money because more people refund than not). >57% refund rate literally makes you lose money from listing. But even if just quarter of people refund that eats almost half of profit.