Price of carbonation canister refills
 

We bought a soda machine a few months ago; since then, the price for
refilling your canister (actually trading in your old one for an already
filled one) has gone from $13 to $15 and now to $19 - that amount to a
nearly 50% increase in the space of less than six months.

Does anyone know if there's a reason, or if it's simply what the market
will accept?

Thanks.

-S-