I pay in the $6-7 range, both LHBS have yeast usually dated within a week to three. Two smack packs (wyeast) in 12 gallons of wort does it for me....even for my award winning Marzen. The yeast starts vigerously pumping out CO2 (only indication on my closed fermenter) within a couple hours and finishes quickly.
I am confused by the pitching calculator (mr. malty) vs. the yeast makers (WL and Wy) on wildly differing proper pitching rates. Why in the world would the yeast makers say "hey, this is enough for your 5 gallons of beer" when they could sell more yeast in a pack and charge more for a proper pitch of yeast? That makes no business sense, and therefore, I surmise that it is actually enough, or the difference (all other fermentation variables controlled/stable, young viable yeast) is negligible to everyone except the high tasters (which thankfully, I am not)....the yeast guys have a vested interest in our beer turning out well or avoiding problems as they already sell a premium product (over dry yeast), but both major liquid manufacturers have chosen to recommend using a less than optimal amount of their product? Why not sell the same pack for $5.00-$6 each, but say the optimal amount for 5 gallons is three or 4 (or whatever it is) packs full.
Bottom line: I am too lazy to wrangle yeast, but would start right away if my option was 6 month old yeast for $11.