When we bought my wife's PRS300 (during the PRS500 $50 trade-in offer), we went to a SonyStyle store and were told that there was also a $60 recycling rebate on the 500. They actually gave us that in addition to the $50 trade-in. We even asked him to verify with his manager that we could stack the rebates, and he confirmed that we could. Ended up with a steal of a deal on the 300.
The point of all that is, if you live near a Sony store it's worth going in and asking about a recycling rebate.