You won't recognize Magic today.
Nowdays, Magic has been highly regimented into formats. Pro Tour events can be in any of these formats, and there are some professionals that specialize in one or more formats and play them exclusively.
For instance, Classic is where all those 'upwards of $70' cards (at their peak, upwards of $200) are in play. Any card from any set is legal, except certain banned cards. Some you can only have 1 of (restricted), some you can have 4 of.
Related to Classic is Extended, the same idea but there are a lot more banned and restricted cards. The banned and restricted cards for these formats are constantly watched, and updated every time new sets come out.
Standard is the latest basic set (we're up to 7th Edition now - at Legends, I believe it was 'Revised', or 4th Edition) and the last two expansion "blocks" - expansions are released 3 per year, one "main" set and two "minor" sets, and they generally have common story-line elements and game mechanics. The first "block" was Ice Age, Homelands and Alliance. Legends - The Dark - Fallen Empires was sort of a block, but they didn't really have a common theme.
Block Constructed is fairly popular, you're limited to the cards only in the latest block.
Limited is by far the most popular format. The entry fees are about double a normal tournament, but you get some amount of unopened product - usually a starter and two boosters - and you build your deck only of those cards. Finals for these tournaments generally hold a "draft", where packs are opened and cards are drafted, as rookies are in sports leagues.
In otherwords, there are lots of different ways to play Magic today :) You no longer need the $200 cards, but if you want to play Standard or Block Constructed, you need to be constantly at work, trading your old cards away right before they become obsolete and getting new ones all the time. Less dramatic, one-shot investments, but more continual investment.
My big problem with Magic: The high level players are virtually all immature snots, and it's no fun to play at anything more than a casual level anymore. The gender iniquity (thus causing Wizards of the Coast to bend over backwards with female-only promotions and tournaments) is also a little irritating.
Oh yeah, the rules have changed. A LOT - no more interrupts, for instance :) They need to be re-read. But they're a lot clearer now.
M.