Yes, most magazine prices went through the roof.
I remember paying upwards of $100 for each pre-ban Glock 21 magazine during the ban (circa 2001).
Other magazines weren't as bad because there were - quite frankly - just so many of them in the states that the ban didn't affect them much over the course of the 10 years. E.g. AR-15 magazines, AK-47 magazines didn't go up too much. DRUM magazines went through the ROOF, however, but this was in part due to the NORINCO import ban.
Meanwhile some other magazines were so prevalent, they were just dirt cheap. FN-FAL magazines; I remember huge bins of them at the gun shows for $3 each.
I'd often speculated that SOMEONE SOMEWHERE was mass producing them in violation of the ban, but if it was being done, it was being done very quietly. You have to keep in mind... MOST magazines are just stamped metal with a spring.. not exactly rocket science to make them. If you took the time to build the proper jigs, and had the proper tools, you could do it out of your garage.
I remember going NUTS when the AWB was lifted - I came "of age" during the ban, so it was like a holiday of holidays to finally be able to order everything I wanted - man, I was broke for a LONG time after that...
Worse than magazines, certain guns also skyrocketed in price. I traded a pre-ban AR-15 for a working 4x4 pickup truck once.
Because of the "lessons learned", any time I get a new handgun or rifle I stock up on "enough" magazines - we're CONSTANTLY under the gun for an assault weapons ban in Illinois, so I don't want to be caught short. Every SINGLE YEAR the AWB comes up for vote in Illinois, and narrowly gets shot down. Just a matter of time before we are screwed over, California-style.
So, yes, I have a PILE of magazines. Even for guns I don't own, which I think I *might* own someday. Paranoid? Maybe. But I'd rather be paranoid and have what I want, than not and caught short.