Depends on the shop, I guess. My local bike shop carries quite a lot of cheap garbage too, but at high markup. I also have trust issues with many such shops. I know some where at least one person working there seems competent, but in most I've been, I get the distinct vibe of employees being domain-clueless salesmen paid to push things (similar to what's typical in electronics/home appliance stores).

I use Google's reviews to check that, always sorting by worst grades first. Saved my ass a few times, especially as an expat.

Such hit and miss are a reason brand loyalty exists, and a reason why people stick to a (certain) shop be it local or a big one.

I got a bike light on ebay and after a few months the battery failed. Even though legally I have 1 year warranty I just can't be bothered arguing with a seller for days and then having to pay return shipping which is almost as much as the light is. I ended up getting a light at the store. Cost me a little bit more but the quality is soooo much better and the battery can be replaced rather than having a sealed plastic casing.

If I ever have a problem with this light its only a 3 minute ride back to the store to return it and I know they won't try and dispute it.

It might be worth reaching out to Ebay and asking for a return—they have ridiculously consumer-friendly return policies, and even if the merchant doesn't want the return, Ebay can force it and hold it against their PayPal earnings.

Indeed. This is part of the reason why stuff on eBay isn’t actually that cheap considering what many people expect

Yes, every time I have complained about something bought on Ebay it has been resolved in my favour.

Plus, bike shop employees are usually very passionate and genuinely interested in your best interest, at least around here, which is not the norm with other businesses. If you're happy with your bicycle, you'll keep using it, and that's more business.

My local bike shop sells bike accessories for like 10x a fair price. Myabe they're struggling, maybe they have expensive rent to pay.

But at some point it's just much too much.

A good local bike shop is invaluable, especially if they have a good workshop.