1) List your item in late September or early October.
2) Use Hi-Fi Shark or sold listings on ebay to determine market price and then go down from 5% to 10%, and more like 25% if there are functional or cosmetic issues. No need to pull a price out of your........hat.
3) Don’t charge for PayPal; it’s against your PayPal agreement anyway and just makes you look like someone who can’t read.
4) Charge fairly for shipping or throw it in. Some folks treat this as a profit center. I wouldn’t even give your ad a second look. If you’re cheating on shipping, then you’re cheating on everything else.