We follow the production procedure that I learned first hand in the Swiss Alps (looking through your website, seems you like old world practices and I agree with the statement that it has a positive affect on flavor and character).
Part of this means that we produce a single cheese from every batch, and as a result the wheels of cheese vary a bit in size -but should generally be around 30# or so. These are maybe 18 to 20 inches across, and 5 or 6 inches thick. The size is important to the quality of the cheese, and if I would split the batch up to make say 3 10 pound wheels then I would come out with a cheese with a different texture, salinity, and flavor profile.
The reason this matters, it's harder to portion out a large wheel into 1/2# segments than a smaller wheel that can easily be cut up (I assume you quarter the wheel, then cut the quarters into 3 pieces) and when your wheels vary in size, so will your segment.
But actually, this causes me to be in favor of doing like you suggest, cutting and pricing regardless of weight. If I cut my cheeses into 48 sections (1/4s, then 1/3s, then 1/2s, then 1/2s) I come up with portions that are approximately 5/8#, or 10 oz. Following your suggested price of $18, that would be priced at $11.25.
Then if I do like you say and also make a slightly smaller size for impulse buyers, I can cut the wheels into 64 sections (1/4s, then 1/4s, then 1/2s, then 1/2s) then I come up with wedges that are about 15/32#, or just under 1/2# (if the wheel weighed exactly 30 pounds) so if I figure this as 1/2 nominal sized, that would be $9 per wedge.
Now I don't like cents. So I could round up to $12 for the larger size that is approx. 10 oz and $9 for the 8 oz size. To make this more fair, the smaller portions would be cut from slightly smaller wheels and the larger sections cut from slightly larger wheels so that you end up paying about the same price per ounce of cheese.
The Swiss often sell whole wheels to locals to have as their own cheese. But then again, they eat the cheese every day. I like the idea of vacuum packing smaller portions when selling in bulk.
Im doing a lot of thinking out loud here, hopefully that will let you help straighten out my thought processes