Maybe you already knew this but I didn't until recently.
When Ebay sends an email for a saved search, the body of the email shows the listing with a BIN price only.
If you click on the listing from there, it correctly shows the listing as an auction for the 30 percent lower price. and the higher BIN price.
So if you list auctions with BIN, the buyer who has saved searches will only see the 30 % higher price and probably will ignore the possibility of getting it for less.
Now that I have you confused - I'll stop.