And how do you make money flogging them at £299?

Same way as you sell coffee for £2 a pop (but usually more) when a whole bag of beans/ground coffee is £2-£3 for 200grams retail price at a supermarket. (lord knows what Costa etc pay)
Same way as you sell a portion of chips in a chippy at £1.50 when a sack of spuds is £7.00. ( I may be being generous)
Same way as you sell a bacon sarnie at the UCI worlds for £4.50.
You charge what the dummies are willing to pay.

EGF above ^^^.
Manufacturing cost has no relation to retail price; Dyson stuff – ex works price is your start point.
Add the following:
– manufacturer design costs
– staff training (manufacturer and retailer)
– shipping including inbound logistics
– taxes and duties
– retailers stocking costs; think warehousing, logistics
– retailer store costs
– retailer staff costs
– overhead recovery and profit margin
– re-investment in R&D
and much more.

Generally the same for Costa; as for local chippie, same principle applies – other than re-investment in R&D

If it was as simple as you make out, business – including manufacturing – would be booming.
It isn’t.

Some people being dummies doesn’t come into it.

Anyway Dyson are soooo old news, why on this very site I am regularly informed that Shark is the UK’s best selling vacuum cleaner.

A bit more detail on the car project, and an interesting fact from the 90’s, Dyson came up with a diesel particulate filter to clean car exhausts, and was turned down by everyone in the auto business, which, with hindsight, looks like a major error…

https://www.wired.co.uk/article/dyson-electric-car-cancelled-inside-story

as for local chippie, same principle applies – other than re-investment in R&D

You’ve obviously never been to any of the chippies where I live.

I was in one on Saturday night and they received an online order for a deep fried , battered caramel Wispa.

That sort of innovation doesn’t come for free.