Cannot keep up with prices...
Most likely once the entire Legendary rush (spawned by it happening last week) ends, the prices will go down. Right now there is a much larger demand than the supply, however that will change given a few weeks. This is primarily due to the fact that people have gotten legendaries, and now everyone wishes to make one.
There’s a big thread about this very topic on top of this forum, complete with Anet’s official response on the rising prices.