Going way back to the OP's question, I only follow two comic book sales sites, Mycomicshop.com and Ebay. (I buy mostly from the former and use the latter as a guide for pricing). And in the past 18 months prices have rocketed and there doesn't seem to be an end in sight.
At MCS a lot of non key Silver Age books are hitting triple digits that were selling for around $25 18 months ago. I'm not sure if this is due to movies and tv shows, but there are times I feel like I'm being priced out of the market.
Last year I picked up an Atom #1 4.5 for around $150. Yesterday a 4.5 was listed for $245.
Avengers 12vg last year was around $25 to $35. The last vg I saw this year was listed at $80 before it sold.
Picked up a Showcase 55 gd+ and a JLA 21gd for $20 to $25 last year. The former just went for $75 in the same grade and JLA 21 passed that mark as well.