Apparently there's some sort of worldwide financial crisis going on, but no-one appears to have told the world's ever-growing legions of retro* MTB fanatics. Just as things like the FTSE and Nikkei track the movements of the stock market, so the going rates for certain sought-after old bike parts keep a watchful eye on the state of the retro market.

Tyres have a special place in the world of retro*. Fairly obviously, they wear out in a more obvious way than many bits. A lightly-used stem or shifter could easily show no signs of it at all, but it's very clear when a tyre's been used, which is important if you're in the game of building box-fresh replicas of bikes spotted in magazines many years ago.

That's all the more an issue if the tyres in question had a reputation for wearing out fast, like, for example, OnZa's iconic white Porcupines. The albino bobbly tread on these lasted for about 800 yards, and they weren't in production for all that long either, so they've become the "gold standard" tyre for the retro* fanatic, with prices to match.

Back in July 2005 a pair went for £122 on eBay. Earlier this year, that impressive price tag was trounced by a pair that sold on the auction site's German wing for €190 - just under £150 at the time.

And if you thought those were a bit mental, you might want to sit down before reading on. For just finished on the hitherto largely unexplored eBay Austria is an auction for a pair of never-ridden white Porcs, which have gone for the mind-boggling sum of €258. That's - really, sit down, or at least hold on to something - £205.

So that's the PorcDex up by 36% since May, an impressive performance given that the FTSE 100 has plunged by 46% over the same period.

Want more eBay retro* lunacy? How about a set of front and rear Paul's Components derailleurs, with anodised rasta colour scheme, plus a pair of XT thumbies chucked in for good measure? $1,233 (£763)...

Once again we're indebted to top retro* community Retrobike.co.uk for bringing these examples to light. Go check 'em out...

* Yeah, OK, just old