I don't know how it is in the US market, but here batteries are quite expensive.
I have the opportunity of purchasing Swiss button batteries that fit the voyager and further models such as 2XS series, 32S, 42S, ...
They should come up to something like 0.96 dollars per unit (to be confirmed). This is, compared to Belgian prices, 25% of the normal retail price (that includes a lot of recycling and various other taxes)
Of course this is interesting only if a certain quantity of these are purchased, so if you're interested, I could arrange a massive shipping.