"We did no mathematical analysis of how the stock should be priced; we didn’t have the skill to do that" Folks may not realize it while doing so, but developing complex gameplay that is perfectly balanced can be considered a feat of linear algebra. So that quote made me smile :)
They actually did a horrible job at making a balanced game as can be seen in the multiple revisions since. I loved it and I'm calling it a roaring success in most respects, but balance is not something I would attribute to the first several incarnations.
If you were playing with your own group of friends who owned a few cards, the small total number of overpowered cards would be a fun diversion. They didn't anticipate the huge success and scale the game achieved. With a worldwide metagame and market for buying/selling cards, scarcity vanished as top players would pay up to get 4 of whatever card gave them an edge, so revisions had to be designed in balance, rather than rely on scarcity to create balance.
Source: I read way too much MtG history a few years ago when I was working on my own card game.