To answer your question yes, most of the cards have been going down.
For instance last year you could find a cresselia lv.X for $60 but now it has went down to at least $20-$25.
Un-like Yu-gi-oh, Pokemon tends to go down instead of up, but it also depends on sets. Like Base set, Neo sets, and some of the EX sets have a higher price range but most of the cards that cost like $60 back then have went down to the $30-$40s.
But your Charizard stayed the average price of $80-$120.
It's because since PUSA is mainly interested in making money off of the newer sets and rotate out the old, they make the prices go down because no one is using those cards. Now that the TCG world is getting more popular they focus on new sets.
Sorry for my rant, but just trying to get it out. XD