The only thing missing is opportunity cost...they spent money on fancier barrels, and those barrels sat in their warehouse for two years. Instead, they could've spent that money on many more less-fancy barrels, could've bottled and sold the resulting beer after a year (or less), then done it all over again for the second year.
If you figure that they could've gotten double the normal bourbon barrels for the price of the 30-35yr Heaven Hill barrels, that means for every one bottle of Rare, they could have produced 4 bottles of regular. When you add the estimated $8 for the box but subtract $1.50 for the extra 3 bottles, you're looking at a $46.50 MSRP. The extra $13.50 was probably hype tax.
Edit: forgot to account for the extra bottles. OCD kicked in, had to edit.