Steve,
$1 per ml seems to be on the upper side of juice prices. If you're paying a dollar a ml, it should be really good stuff. As for "Bang for the Buck", try VaporRenu.com. Totally USA made e-juice. Custom made, PG or VG blends are around $6.99 for 30ml. Bests the crap out of $55 a carton! As for trust worthy, check out YouTube or scan the forums, if other people are talking about them, chances are your transaction will be a good one. And YES, you can simply drip into your used carts and they're as good as new again.