I've bought and sold for many years and have had very few issues.
If you're worried about lost packages then UPS is very cheap, especially when you use the eBay negotiated rates. It's practically 50% off published rates.
Also, I know everyone wants to say pack well and packing well is important but make sure you use an appropriately sized box. Even before COVID, everyone bulked out before they weighed out (meaning they physically ran out of space on the truck/plane and not because they were overweight). Larger boxes will cause you to have dimensional weight applied. There is no such thing as a 1 pound 16x12x12 box. That will automatically get converted into a 8-15 pound rate.