Newegg has the Icy Dock FlexCage MB973SP-2B, the model we looked at today, for $96.99. The same unit without USB 3.0 costs $10 less and is available at Newegg as well.
The price doesn't make this FlexCage great value for those without a specific need for a drive cage. It does fill the need for those of us with spare HDDs that get swapped around different machines often. If you pull drives from one machine to use in another quite a bit then it would make sense to buy a FlexCage for each of your computers.
The system performs well and adds a nice level of convenience for users. In our tests, the HDD actually performed a little better inside the MB973SP-2B than it did just sitting on a desk. I can't count the number of times I've formatted or read data back from a drive with it just sitting on desk. What I never considered is how bad the vibration is to the HDD. If just sitting on a desk is enough to slow the drive a small amount, then it can't be good for the delicate components inside. If you have data on a spare drive the chances are it's important data, so putting it at risk isn't something you want to do.