I can understand that. Then there is still ebay which is pretty safe now with their buyer protections.

I've been buying and selling bike stuff for only about a year, but I can tell you that it is almost always better to get durable components second hand (i.e., crankset, frame, wheelset, handlebars, stem, seatpost) and let the seller eat the depreciation. You get much better stuff for your budget that way.

I mean, unless you somehow don't get obsessed with your bike and have a weekly urge to tinker and improve it...