Best deal for these so far has been Gamerush. $11-12 for DK1 and Dk2 bundles. $14.00 for the DK Jungle Beat bundle. I bought an extra Jungle Beat bundle for the extra bongos, then sold the sealed game on Ebay and got like $15 so the bongos were free.
I kind of regret buying these for retail at Best Buy when they came out, but I was afraid they might sell out and end up hard to find. Plus, we got a year of enjoyment out of these at parties, so that was probably worth the extra $30 each I paid for them.