FYI Target clearance drops: 15%, 30%, 50%, 75%, 90%, then to salvage. So the question is do you think the reader will on the shelf when it hits a lower price point. It's a game I play all the time. One end run if they have multiples is to buy one, but don't open it. Wait a couple weeks for the next reduction round and if they have it buy it again and return the one one you bought earlier (still unopened). That way if they do sell out you still have one.
I've HEARD that Costco is selling the 505 for $179, but haven't actually witnessed one there. I know they sold the 500 when the 505 first came out. If you have a Costco membership or know someone who does it might be worth checking out. If you don't have a membership you can check out the inventory by going in the out. If you don't see a display ask at the electronics cage at the front.
Alternatively, Best Buy will have the 300 on sale this week for $225 w/ cover and $25 Sony e-library GC. Personally I think the 505 has better ergonomics.