@Madmax1993 as a shop owner, i agree with some of what you say but not all, i absolutely agree that you don't have to support a crappy shop owned by a crappy person, i think most people would agree with that, those shops always eventually disappear, but advising customers to buy online? risky, you would literally be giving out advice and telling someone to buy elsewhere, now to a point i do do this, for example i don't sell e bikes, too unreliable generally for me but i tell people how to buy them, where to buy and what to expect, and which ones i can't/won't service/won't even tolerate in the shop, but that's more to ensure i don't have to deal with the crap ones as opposed giving advice on a particular bike.
while also shops do have the ability to charge labour that too has been eroded as customers already want to pay mail order prices, so if you quote parts plus labour rate they'll never go for it, so now at most it's retail price and free fitting (which for context i do on high value parts or bigger parts bills) but bluntly, people do not value knowledge and experience anymore, generally, not just in the bike trade, that customer just wants to pay the least they can get away with, and i get that money is tight, no one knows that more than me, i'm 48, i don't own a house, have no pension, and i pay myself £350 a month and £250 goes to the olds for living with them, but i'm staring down the likelihood of van life at some point as my mum has just gone in to care, long term that means the house is going (unless she's passes in a short time) i am not by any means flush, but i have a few nice bikes, that technically the shop owns. so i'd hope people would support my shop, i think i'm a good shop owner, and i think i have a good shop, and a lot of my customers are friends and i do everything i can to ensure repeat custom. but long term i'm probably f*****!
your suggestion about fitting parts from online, always issues there, currently one of the biggest being counterfeit crap, you fit it, it fails, they moan at you, because they don't want to believe they got stitched up, they'd rather believe that it's the fitters fault as it's easier to moan at them than some far eastern website. assuming they do get a genuine part quite often it's the wrong one, advising to them to get the right part but not from me to fit it for cheap labour? i'd rather not. also cross warranty issues, hmm . . . all a bit of a nightmare to be honest.
also i literally had a guy in the shop the other day, i ordered the tyres he wanted, they were an odd size, quoted him retail price of £70 each, he immediately said i can get them cheaper online, i said i'd fit these for no labour, he agreed as he was scared he'd damage his carbon rims, the next day i phoned him to tell him it was ready, he asked about clip on mudguards, i suggested SKS raceblades, think they were £55 and i said i'd fit them for that, in that time saying that he was already online saying i can get them for £40 from whoever online, he waited for me to suggest an option because he didn't know what to search for online and didn't know a brand name and immediately went to a mail order site to compare and try and push me cheaper, i said i wouldn't fit them if he bought them (mainly because i simply felt he was being rude) and don't forget it's not that shops are over pricing stuff (not generally) it's mail order that as you say has economies of scale and choosing to make smaller margins to justify their business model but people have convinced themselves that mail order is a retail price and shops charge over retail prices as opposed to shops being at retail price and mail order having a discount, while i understand in real terms there's no difference in the outcome of that previous sentence it's a mindset thing, "the shops are expensive", no, mail order is discounted, my point being there is a difference and effectively the customer does have that wrong despite it sometimes being to their benefit.
i'll also point out one other related thing, a few days ago on a local facebook group page a lady asked "what type of shop would you like to see open up locally?", i thought this was a stupid question to ask as it turned out she was eyeing up a shop unit in a small town near me, basically she wanted a shop and was asking what people would buy, now this seemed odd as obvs i knew i wanted to open a bike shop, she's asking what do you want because i'll do that, and that seemed silly as what if you then open a shop in a trade you know nothing about! anyway, people replied and listed all the types of shops that had previously been in the area, butchers, bakery, fishing tackle and bait shop, wool/knitting shop, and the list went on, all these types of shops had been in the area previously and had not been supported and faded away once the owner got demoralised and couldn't survive. my point here is people tell you what they want then don't use it, don't value it, and if they do they then say they can get that online cheaper, it's not just bike and bits, it's everything, it's extremely hard fought.
retail is not an easy trade to be in. most days i enjoy it but some times people can be terrible to deal with and they seem to have no idea how they come across to others.
sad really.