Francis himself said he's down $15M by simply not signing the contracts offered to him since Stipe. He made $10M for Fury.
He's presently -$5M instead of fighting for the UFC.
His manager said he'll make another $10M for Joshua. That would put him him +5M yes... except had he signed with the UFC, fought Jones, and then kept his present schedule of fights then in October and March he'd be on his 3rd fight by now instead of his second. $8M purse so long as he kept winning would've put him at another $16M for a total of $31M.
$31M > $20M
He did complain if he lost his pay dropped from $8M (as he'd no longer be on championship pay), but they never told us to what. It's fairly safe to assume though that it would be much more than the $600K he was making before hand, which was only so low because he was refusing to sign a new contract since Stipe, but even on that that he'd make $1.2M just on the lowest possible end for 2 fights.
That would put him at $16.2M < $20M. If he however he dropped to something like $2-3M a fight he's at $19-21M <=> $20M.
If he gets a 3rd boxing match and has another $10M pay he's at $30M < $31M he could've been at with the UFC.
So yes, he's down by not having just fought in the UFC. He also turned down a guaranteed $20M from ONE which is more than he's made in boxing too. Which is why I don't buy his excuses and instead think he's simply done with MMA, whether because his knee never properly healed (IMO as that injuries when he stopped with MMA and said he wants to box) or he just prefers boxing only.