*rubs chin*
*does maths*

You're right.

My working...

In 2003 Deluxes (known as Max-Cons) cost about $25.
Disclaimer: I'm working off the Japanese RRP but IIRC the AU RRP wasn't too different, so give or take a few dollars.
This year the price of Deluxe figures has risen to $35, representing a x1.4 price rise.
If Commemorative Series Rodimus Major cost $35 in 2003, then 1.4 x $35 = $49, which of course rounds up to $50.

So yeah, it is on par with the rate of inflation for Deluxe Class figures. Other size classes have also risen in price, but it happened a few years ago. Remember when Scout Class figures used to be $15? They're now called Legends Class and they're $20, so that's a rise of x1.3. And the cost of Voyagers (formerly known as Megas) and Ultras also crept up during the Unicron Trilogy years. Voyagers now sell for the cost of Ultras and although it's been a while since we've had any Ultras in stores, they did sell at $70.

I guess it's like being a frog saucepan.