It's not about inflation, it's about supply and demand and collectability. If it has an appeal to collectors then the price will rise as demand increases. The more limited in numbers, the more people are willing to pay so that they can say that they own one.
It's a prestige thing - just like diamonds. Although diamonds are about as rare as cubic zerconia, people percieve them to be rare and thus the high price tag.
With the NM XLR, they are actually numbered and certified so you know exactly how many are in existance. And with the high demand for this car right now, I'm surprised the prices are not higher than they currently are.
Personally, if the XLR came out at $100K, I think it would still be a bargain, but that's just my opinion. And I bet you there are more than 101 people out there that have the money and would say the same thing.