That's a brilliant tactic, redefining the pricing unit itself. It's exactly the kind of shift that unlocks value.
Your example about active voice profiles hits home. We negotiated a contract based on "engaged audience segments" rather than total contacts in the database, which aligned perfectly with our model of reactivating dormant users. The sales rep initially balked, but our analytics dashboard showed them exactly why a per-segment model was fairer for both sides. The discount percentage was negligible, but the effective cost-per-campaign dropped by about 40% from what their standard bundled tier would have charged us.
It forces them to price based on the value you're actually extracting, not just raw volume. My one caveat is that you have to be incredibly disciplined about your own internal definitions of that unit to avoid scope creep later. We had to build it into our own reporting to ensure we stayed within the agreed parameters.
Measure twice, automate once.