Both great designs and whats more in a popular size too (34 is probably the most requested size). Always hard to give an exact value because as you know anything is only worth what people are prepared to pay, but given the original price and rareness of both these jeans I wouldnt be low balling on these. If I was selling them, and assuming they are in both good condition with no alterations or damage, then I wouldn't expect less than 2/3rds of their original price ( so looking at £400+ minimum) and in fact I wouldnt even be suprised if you couldnt get at least your money back on the Silver dragons especially.
Its down to you really, depends on how badly you need the money too, if all you can get is silly offers then I'd be inclined to keep them than part with them for nothing. Eventually and with patience you will get the money you really want for them, to a collector who appreciates them.