Price hasn't changed because the Supply and Demand isn't there, IT will if that changes.
I don't know actual numbers, but both supply and demand have increased through our shop over the past 10 years for these engines. Numbers at the sprint tracks have increased tremendously over that time period as well. Numbers on dirt have increased, albeit not nearly as fast as the clone has. It is starting make some ripples though.
Each year, our new 206 sales get stronger, and our rebuilds are off the hook right now. At $135 (parts & labor) for a complete rebuild, it's no wonder.
Personally, we've held the price in check on new engine packages for the past two years simply because we are wanting to promote the class.
Price from the factory has certainly increased (the normal percentage that Briggs typically does I assume.)
Chain guards, throttle kits, air filters, all have had slight price increases since the 206's inception...it all adds up.
After the swap meets and shows (March or so) we'll have to raise our prices some, I'm sure. Until then, we want to help our customers and grow the class as best as we can, even if it means sacrificing a few bucks here and there.
Funny thing is, we're still building plenty of flatheads, (new & used,) and I believe that is a direct result of the clone implosion.