Just a few thoughts........
1) all gear is used after it’s first time in the water.
2) most divers take good care of their gear because their life depends on it.
3)many LDS will tell you that used gear bought "online" is substandard because it might have been used by someone who didn’t take care of it.
4) most LDS have specials on their "used rental gear" for divers on a budget.
5) properly trained service techs are trained to repair and bring "used" equipment up to the standard that it is safe as a life saving device.
Seems like a double standard to me for a LDS to refuse to repair an item bought "online" because it used and can’t be depended on but will sell you used rental gear.
I have bought many items online and yes from the "terrible" E-bay..... and I have bought a lot from my LDS.... I have had the same great service from all my equipment...... because I take good care of it and because I have it serviced regularly. Not because of where I buy it. If LDS don’t change their attitudes and their "customer service style" there will only be online stores..... times are changing.... A wise man once said... A tree that doesn’t bend in the storm ...breaks...... ooooo and about that "online air" that all the LDS like to through at you....... I went online and bought a brand new compressor and now fill my own tanks..... and yes I am certified for it. Do all my own tech repair now...... and only because of my LDS’s attitude toward customer service...... I will add...not everyone has a natural skill or aptitude to repair scuba equipment and many have NO BUSSINESS even trying to. If you aren’t certified to repair equipment then DON"T!! You will be risking your life and maybe that of your Divebuddy. This is just what works for me and my situation. Be safe and dive often.