It's Australia Day on Tuesday so let's talk about bikes.

While the market, the dollar, commodity prices, the yuan, your superannuation and the value of your house have been going down, motorbike prices have been going up faster than the petrol pirates' bank accounts.

It all started in September (my birthday, thanks for forgetting) when Shannons sold a Harley-Davidson 1927 FHA 8-Valve V-Twin racer with its scramble-type side car for $600,000.

Last month it was over to the South Point Casino and Exhibit Hall, Las Vegas, where Mecums sold 516 twin wheelers for $13 million. No wonder there was excitement in the room.

Mecums didn't sell anything for $600,000 but they did hammer down one of the rarest bikes in the world, a 1912 Henderson Four for around $200,000.

Naturally I was there for the 2004 MTT Y2K Turbine from Aussie Allen Smith's collection. Powered by a Rolls-Royce Model 250 Turboshaft, more often found in helicopters, the small rocket ship is good for 360kph.