well, it all depends on BIN price that you added. I do agree that bidding mostly end in higher $$$. So, if you add a price, there will be no point for a bidder to bid higher than BIN price...
i have tried this many times. on so many occasions someone has bid so the buy now was removed automatically, and the bidding went higher than the buy now that was on there. my advice, stick with one or the other. but not together.
I use the BIN often but you have to use it wisely. First you must "know" what the item is worth. Price it where someone who is willing to pay the price and not wait can hit it and get it over with. I often pay a little bit more to BIN just so I don't have to wait to save a couple of bucks. And you need to start your bidding above what someone trolling for a CHEEP deal will bid or will will go away to quick. If your items get much higher bids than your BIN, then you are doing something wrong in your pricing.