I just tried to buy a 2012 Prius V with the Costco program, and it didn't work out. The Costco web site says you can get invoice plus $200. Taxes and destination are always added in after. But when the dealership showed me the invoice for this car, they had added another $1000 in miscellaneous fees before they added on the $200. So I walked.
The lease on my 2010 Prius is up in April. A bigger one would have been really nice, but mine only has 21,000 miles so I will buy it and not look any more. I hate going to dealerships and sitting and waiting for hours while you haggle.