I am basing the X-Men #1 and JIM #83 comments on what I have seen for the mid to low grade prices over the past 5 years or so. These are a better reflection of collector interest IMHO since the average collector can still afford them. Not all of us are fortunate enough to play in the high end like some board members.
As far as X-Men #1, the first movie came out in 2000 and the second one was on the way (released in 2003). You could still pick up FN copies of X-Men #1 for less than a grand before the 2000 movie was released. And, looking at GPA, 6.0 copies ranged from $1,380 to $1,950 in 2003. The big jump in this grade actually happened last year according to GPA, with the price going from a high of $2,390 in 2007 to $3,761 in 2008.
Yes, in high grade JIMs took off due to the perceived scarcity, but I would argue that the prices on JIM #83 in 6.0 or lower did not until after the movie was announced. Looking at GPA, the 2007 average for a 6.0 was $2313, and in 2008 it was $2881. The current 12 month average is $4229, with the most recent price being a copy that sold this month for $5205. Going back further, the highs for 6.0 copies recorded by GPA were:
2003 - $1503
2004 - $2225
2005 - $2005
2006 - $2151
2007 - $3250
2008 - $3300
2009 - $5205
When you look at their average price chart, it shows steady growth until a sharp upturn in mid-2008.
Even in 9.0 the slabbed prices for JIM #83 did not take off until 2007 or so.
2009 - $27,800 (1 sale)
2007 - $19,120 high, $15,558 low (3 sales)
2006 - $11,500 high (1 sale)
2003 - $13,000 high (1 sale)
2002 - $13,225 high (1 sale)
Looking at these trends, 2005/2006 would have been a good time to buy key SA Marvels if you missed the boat in the mid/late 1990s.