Just before the last E3 there were a lot of reports that said that all three current hardware makers were expecting a war of price-drops at E3, and that all three of them were ready to counter any competetor's price-drop announcements with their own price-drop announcements.
Sony (which had the PS2 at $200) kicked things off by announcing... that they were making a new version of the PS2. With like, a progressive scan DVD player, a quieter fan, and the network adaptor built-in. It would be $200. And so they dropped the price of the "old" PS2 by $50 just to clear them out.
Microsoft (with the $200 XBox) decided that the addition of extra features, and the clearout of some stock, wasn't really a $50 price drop, especially since the inclusion of the network adaptor was just a move to try and get more even with what the XBox normally offers. So they put out a simple $30 price drop (IIRC).
(I can't remember right now if either the PS2 or XBox are/were coming with free games at the standard MSRP.)
Nintendo had the GameCube at $150, coming with your choice of one of several great games, each with a MSRP of $50. But games always tend to get cheaper with time. So at E3, Nintendo expanded the selection you can choose from to include the $50 GameBoy Player. Since it's hardware, it quite unlikely to drop in price. So it's a more "real" $50 added value.
It basically comes down to almost nobody at E3 having had any "significant" price drops. But they were all ready for them. Which is why people are speculating that there are more looming on the horizon. And Nintendo offering to let people skip the $50 bonus item, and just take the $99 GameCube, is the most obvious idea.
It's like, people can say... that Sony should drop the price of the newer PS2 to match the XBox. But without deep knowledge of Sony's financial situation with the newer PS2, that opinion doesn't mean squat. Sure, a price cut is good for sales, but is it worth the tradeoff? How can you know unless you know exactly what the tradeoff is?
The $99 GameCube is a very simple idea right now. So everyone is expecting it.