A lot more:
Based on our good friends at Wikipedia:
List of Magic: The Gathering sets - Wikipedia, the free encyclopedia
There is 1 core set released each year with about 250 cards. These cards are mostly old cards that get cycled in and out of the base set. Back when I played they did add a few new cards to the base set though. But mostly they're re-releases.
In addition to that core set, it looks like they've been doing 3 expansions per year. One big expansion of over 200 cards and two smaller expansions of around 150 cards. My numbers are actually on the low side just because I like nice, round, numbers.
With that being said, I have no idea what the quality of their releases are like. Looking at the wikipedia page shows me just how long I've been out of touch with Magic. My last expansion was Weatherlight, a smidge of Tempest and 5th edition. Since that time, it looks like 50 (FIFTY!) expansion have been released as well as 11 core sets.