But despite those 40% price leaps, I can assure you that their margins are very tight.
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Some of my job involves an amount of bean-counting; out of curiosity I had a look at Ultima (Powacycle's parent company)'s annual reports - for a medium sized company listed on the LSE, the profits are indeed fairly modest despite strong sales and the bikes are to an extent cross subsidised by the sales of low energy lamps, computer equipment and software and other electronic items.
I expect the same cross subsidies happen (on a larger scale) with the Japanese and Chinese factories, at the British end the other dealers in e-bikes seem to be very lean companies with just a handful of staff (and are doing very good work customer service wise all considered!)
As for the DIY bargains, I expect if you costed in the
time of very talented and experienced British engineers with often 35-50 years of work experience and knowledge who are constructing these wonderful machines, they would soon approach the cost of the mainstream bikes.