Huh. This is a great price, it's actually cheaper than buying an internal-to-external bracket and associated cables. I've got one of the SGI Rackable DAS boxes for my backup drives hooked up via a long internal-to-external SAS cable running through an empty PCI slot to an internal SAS port. Not the best solution but it does work.
The only caveat with purchasing another HBA for this is that they tend to have high power consumption even at idle (10-20W in my experience). Looks like LSI specifies 13.5 watts for this one. Also, these are getting a bit old, and "only" do PCIe 2.0 x8, so 4GB/sec half duplex. That's plenty for spinners unless you're hanging a ton of drives off expanders. I might buy one just to have it, although I do have some 8-lane internal SAS cards sitting in my parts box already...
Edit: Aaaaand it's gone.