That said, being no stranger to online purchasing of fine outdoors and shooting gear and clothing and not living in an area where many things can be looked at before purchase I orders lots of stuff online and quite often will order two or three items, keep the one that I want and immediately return the others. Due to the amount of online business I conduct, I am also very aware that a flat 10% "restocking fee" is not the industry norm.
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On many smaller orders, most of the times these days margins are thin enough that it's actually on the borderline on if it's profitable to sell it to you or just stay home. Not even counting shipping, just the labour charges and packing material to ship an order properly, then to inspect and repack, it's actually sometimes a fair bit and no point putting up with that because somebody wants to use your company as a buy & try place. Getting a return might easily mean having made a loss on the order so why even bother... unless you are loosing shareholder money it's not sustainable.
Our company actually just simply scraps quite a bit of lower end cheap stuff we get as part of bigger lots, as it's not worth selling because one or two people on eBay lying to use you as a try and buy place pretty much make it unprofitable to sell the entire lot, If your actual profit on a $17 order might be $1 but some person returning stuff while lying about it winds up costing you $20 might as well just not bother selling those and scrap them, or keep them to sell at next to nothing as a big bulk lot to other companies that work in the grown up world where purchases are final.
If you actually made a mistake and purchased something in error in good faith and need to return it and exchange it for what would work, then that's a bit of a different matter most of the time but ordering multiple things regularly with the intent to return those you decide you don't want is quite a bit different.
I think what you are seeing is the difference between hardworking small business owners, trying to make a decent living & provide decent paying employment for their employees, that have to deal with people doing that and the "I deserve to do whatever I want to do and find somebody else to pay for it or take a loss, I'm special." type of modern consumers.
Here is a question you should try asking yourself honestly:
If you buy something "new" and somebody else had gotten it sent, looked it over & then returned it, then the store had carefully packed it up as best they could, are you happy to get as "new" at full price?
...I'll bet you won't but who knows...
In this Amazon.com/internet shopping day and age, vendors with a shit/nonexistent return policy, restocking fees or the lack of real time website inventory (looking at you TNVC) are at a disadvantage. While there are holdouts, these too will become things of the past as having to compete with a company that doesn't have a shit return policy or a restocking fee for the same item is a losing situation.
In the long run, being comfortable with what would happen if I did want to return something and not have to deal with shit like restocking fees or a hassle as to if I can return it actually has me buy more things from you/in general.
Actually you are going to be in for a huge surprise once the online shopping options are fully consolidated into a few big companies. Everybody in the industry knows these overly generous return policies for people are unsustainable, the big players just put up with the losses long enough to drive out the small business owners that can't afford to loose other people's money and then they will tighten up just as soon as enough idiots only buy from them to drive all the small players out of business. All you are doing is helping the new Technocrat overlords build your own straightjacket.
You mention Amazon as your example ... well guess what..... try doing a bit too much of the buy & return on Amazon and don't be surprised if once you hit a pre-computed limit of where the algorithm says you are not worth having as a customer, they close your account permanently. Google it... they are getting aggressive about it now that they are the big top dog in the online shopping world.
Walmart and many others are now also working with specialized firms to track customers across multiple retailers, prone to return stuff a bit too much and "encourage" them to buy & return somewhere else... information also easily searched for.