Pounds, like everybody else.

When you remove the auto-forage step, you force the player to pay for (some) corps which could have foraged safely via auto-forage. This results in costs no lower than Marshall's model, and many times far higher.
Go back to your god in this: Original EiA. What happened at the end of a turn? People would figure out which corps could forage safely, and which corps could not. Then, they would make a financial/strength decision as to whether the cost savings by not foraging outweighed the risk of foraging.
THEN, on the next guy's turn (frequently), aplayer would say "Oh, I forgot to forage that corps", and promptly pay another buck or two or else forage the corps. Note that it was HIS choice. What your model would force, if applied to the board game, would be to force the player to pay for supply, no matter how stupid that might have been during the turn, simply because he didn't notice it while moving.
Marshall's model does it EXACTLY the way it was done in the board game: Cut the player a little slack (let corps forage, if they can do so safely). But, there's a problem: the computer can't be as free/loose with the rules; at the end of a turn, the computer MUST decide what to do. Marshall's decision was simple and obvious (and correct, IMO): Corps that can forage safely SHOULD forage safely.
What he missed was that some corps would now forage even though the player really would like to have payed for supply. In the board game, it was obvious where the attacks were, so the corps in the attacking stack would all get paid for. But, Marshall apparently didn't code to notice this, and applied the same process as he did with all of the other corps on the map. THIS is the problem that needs fixing. The main model MUST stay like it is, because it is exactly correct (i.e. mirrors what a human would do if presented with a choice). Only the end-case needs fixing.
At LAST! The greatest campaign board game of all time is finally available for the PC. Can my old heart stand the strain?