One is the broken window fallacy, or the notion that disasters are somehow good for the economy. (While they do stimulate production in the short run, an economy would still be better off not having a bunch of stuff get ruined and having reseources devoted to growth rather than replacement.)
The other is the concept of price gouging, or raising prices in response to increased product demand as a result of crisis situations. The non-economist consensus seems to be that price gouging is bad, as evidenced by the fact that it's illegal in many jurisdictions, but economists are on a mission to (rightly, in some ways) make the case for the benefits of such a practice. Matt Yglesias presents a well-reasoned analysis over at Slate, for example. In addition, I made a handy little primer on the economics of price gouging to help you work through your logic.