Will need a follow up from someone who's active, or at least spent more time in-game than I did.
Jita's the busiest economic hub in the game, so they're effectively shutting down a sizable chunk of the game's trade. Though it's in a secure area, inasmuch as the in-game police will kill you for attacking other players, so many ships are involved that they can just suicide attack even the larger vessels before being stopped.
I doubt this will actually "break" the economy though. I imagine it will be disrupted for a time until the campaign ends or trade moves elsewhere.
To be honest, the overall market effects were trivial. The one thing that did happen was the actual trade that happened in and out of Jita (the biggest trade hub in the game) was virtually stopped as the volume of trade for raw materials pretty much stopped. The amount of transport ships reduced to a relatively tiny amount.
Despite all that, there are a number of reasons that this won't have a big impact overall. The thing only lasted for 3 days. Lots of people will just go someone else to buy their stuff (there are several other trade hubs in the game) or will just not buy stuff those days. Another reason is that this event was announced months in advance. Many people stocked up on the things they need to keep their personal industrial machine running. I suspect the incursion would need to continue for at least a couple weeks before you see any sort of market crash. Plus, there are always other places to go. That trade hub would die in a sense, but that might only marginally affect the overall economy.
