I believe there's an error in that spreadsheet.
It's computing FV as CV * (I * Days/365) - DivRate.
So it's basically computing the fair value as cash value multipled by the interest/carrying cost for the time remaining in the contract less a nickel (the 5% index dividend that's being used as a default).
This produces too high a result. For instance it would compute a fair value premium of over 12 for the March S&P contract which as of today should only be only about 1.50-1.60.
Instead I believe the formula should be:
FV = CV * (I-DivRate) * Days/365
The net cost of carrying the underlying equities (which is what the fair value premium is) is the difference between the cost of money and the dividend realized - which is a net of around 0.65%/year right now.
The factor above and below FV premium for buy/sell program activation will be slightly different for each firm due to differences in their respective cost structures and is probably premiums between $2.75-3.00 for buy programs and $0.00-0.25 for sell programs today.