Well boys and girls, I took the liberty of breaking into the DOND game on the NBC website to see how things were calculated, and here's the rough overview..
The board is divided into two tiers: the LOWER tier (consisting of all values under $100,000), and the UPPER tier ($100,000 and above).
In order to calculate the bank's offer, you need to know the "official percentages" of the show. To keep it simple until we figure out if they use the same numbers on the US version, I'll play out something from the Dutch version [which, BTW, is where this game originally was used - it's even got the MILJOENEN JACHT logo in the game].
In Round 1, the percentages are 5% and 6%. So the player eliminated 4 cases ($1, $10, $100, and the $5,000,000), to give the tier totals of $176575.71 and $5000000 respectively.
The sum of the LOWER tier is multiplied by the first percentage (5%) to make [8829].. then the sum of the UPPER tier is multiplied by both percentages (5% * 6% = .3%) to make [15000].
These are added together to make the bank's "offer" of, in this case, $23,829 (as confirmed with the show in question).
The programmers of the DOND game actually made a mistake.. they miswrote the array of percentages.. so the online game actually starts with the percentages for Round 2 in Round 1.
I've tested the formula with the Dutch show, and it works well.. but so far I haven't hit the Aussie ones on the head yet - likely using a a different TIER FACTOR.. [okay, it's a bad NBC joke.. ]
I've had our own FLASHGames² version in the works, but since it seems they aren't in need of that now, maybe I'll convert it into a "Banker Calculator" to play along with the show..