Something to consider:
Selling on ebay is NOT what it used to be. One could say it has evolved, from favoring the sellers, to putting things in place to protect the buyers, to now somewhere in between, but still favoring the buyer. The scams, the 10% cut that ebay takes, in addition to the 3% that paypal (owned by ebay) takes, and exorbitant shipping costs drove a few (including myself) away from considering ebay as a place to sell. Still, if you are looking to maximize your investment, it may be the best choice, though, like others have said, the runaway costs for many of the OOP boxes have gone down. You could do Amazon, but they also take 10-20% off your total, depending on selling price. Or you could list them on forums, such as this one.
I no longer think music buying as investments a viable option, but that is just me. I did it for over ten years, saw some good things come out of it, and moved on. Now I am downsizing my collection and concentrating on enjoying the music that interests me.