If using water based, I'd say Bona Traffic is the best way to go, but yes, it's more expensive. Alternatively, maybe Bona Mega.
I would explain the differences between oil vs. water in durability (and price) and explain how much extra it would cost to use Bona Traffic so that they can make informed decision.
BTW, when I gave an estimate, I do specify if water or oil based and this helps both communicate the benefits as well as protect me for later if things change.
Debbie Gartner, aka The Flooring Girl
http://TheFlooringGirl.comWestchester County NY