-
there are costs to doing business in person...If they sold everything online they wouldn't have to pay any of those costs
We're talking about a business model based on a shop which does mail order on the side. Maybe there's a small saving on mail order because the goods don't have to go from the storage area to the display area on the way to the customer, although for small parts the journey is more likely storage to counter so there's no difference. Clearly the economics are different if you're a warehouse operation with no shop floor, although the actual cost of p&p is still going to be £3-£4 on top of just throwing unwrapped bike parts onto the loading dock, and that money has to come from somewhere.
But like I said there are costs to doing business in person too; eg. dealing with cash, having a guy standing around on minimum wage to help customers and prevent shoplifting, having a neat, clean, well-lit shop floor that isn't putting you at risk of a lawsuit, etc. If they sold everything online they wouldn't have to pay any of those costs, and if you're factoring in jiffy bag costs to P&P you arguably need to factor in shop floor costs into shop floor sales. Or, just shove all those costs straight into the margin and charge less for postage.
Anyway it's all moot because like I said it's next day signed for delivery which probably costs them £6 already without handling (it's >£7 with Royal Mail according to the guy) and I don't mind paying it because it's still the cheapest option.