Gold PLATED? For a hundred and fifty bucks, that SOB better be gold through and through... not just plated. Although that would present problems with the heat these pumps can see... that spring might lose it's "spring". Titanium, however, might hold up, and fetch a fair price... although thats generally used for light-weight applications, and I'm not sure how much weight you'd need to shave off of a tiny little spring thats only an inch long... . Diamond? Wouldn't make for much of a "spring" though.
The logical explaination, is that this particular spring has been blessed by the Pope, autographed by Axl Rose, and was once featured on an episode of Melrose Place... . either that or the price of steel went through the roof overnight... . in which case, I'm a millionaire.