[jodrellblank]

Yes it is, that's why you can get a bike from Walmart for $200.

This is like asking why new Mercedes costs so much when your used beater was very cheap. Last year Ford sold 4,500,000 cars. Honda sold 1,430,000 cars. Brompton sold 85,000 bikes. They make them in London, not overseas, so that costs more, and they don't have the economies of scale that car companies have. Brompton are also a luxury brand, with a reputation for a quality product that can last decades, they're not aiming at the low end of the market.