Are you buying a custom gun, simi-custom, off the shelf? Left hand guns will limit you to a specific price range which will roughly fall between $250 and $10,000. This being the case, you can buy a very good .22 for the base price indicated, meaning that anything above that price would be less economical?
Are you buying cheap .22 shells from Wally World or the good stuff from Elly? That will affect comparison.
Are you going to cast balls or buy pre-cast or swedged? this will also affect price.
Are you going to shoot Swiss brand powder or Goex or Elephant? Swiss is twice as expensive per shot, that will effect economy.
What I'm trying to say is that BP shooting is a very individualized actvity and economy for one is wasted money to another. Do not limit your decisions based on 1/2 cent per shot difference in price.
Believe me, your .32 will do things a .22 never dreamed of accomplishing! Don't worry about duplication of .22 balistics, that is no sweat at all. Consider the virsitility! With moderate loads you can easily duplicate .22 mag, .22 hornet, 22jet figures plus covering the .32 pistol cartridges including the .32 magnum, and with a stiff load probably come near duplicating low level .357 balistics. (I haven't checked the book,I may be off on the figures) The versitility is a key decision making factor.
If this is your first or only BP gun I would suggest going to at least a .40 cal to increase your usability of the firearm. Most states will allow a .40 for deer hunting and it does an equally excellent job on small game and uses only a smidgen more powder and lead than the .32. If you are breaking the cost down to the per shot point you might need to factor in the fact that you will have to buy a new weapon $$$$$ if you ever decide to hunt something bigger than rabbits.