Too quickly? I'd say not fast enough.

Not just the price, but if you flood the market with 'collectibles' then they all become the ordinary, and aren't so collectible.

The new KB Videos coming soon.

Nathan makes a few good points.  I often have to explain to customers who are surprised by the prices that Lego bricks are primarily made in Europe, and since they're a by-product of oil, they get expensive, because in Europe their oil problems are even deeper than in the USA.  Also, Lego has been doing other things to combat inflation.  More pieces are put in smaller boxes to conserve on packing costs, for instance.  They've opened a factory in China and one in Mexico to more readily ship to Asia and North America, respectively.  Considering that American inflation has been 9 to 11 a year since 2011, Lego sets are still pretty fairly priced, and $99 sets are being geared toward younger builders increasingly.  The LEGOLAND Main Street in 1980 was $40 retail, and would probably be $90 to $100 today.  In 1980s dollars, it's like buying a $100 set.

I think it depends on 1: What the theme is 2: What the set is. The reason the Falcon is now over $1000 on the after market is because it is a much loved ship and it is to scale with minifigures. For the modulars, they were and always will be fan favorites, just by their nature of being able to connect and build a larger city. With the Tower of Orthanc I think the price will go up greatly after it is no longer available because it is from a theme of which most people (myself included) think it did not end on a good note, and thus this was the best set from that last wave and will go up in price. I think hard core fans of any theme will always fork over the money needed to buy something from what they love (Like when I spent $400 on the Death Star that I can't brickfilm on!!!!). And until the fans stop buying USC sets, Lego won't stop making USC sets.