Yeah, it will depend on quantities and such. But I think it's highly unlikely that, by the time the broader situation is resolved, Apple won't owe Qualcomm more in royalties than Qualcomm owes it in BCPA payments - that is, unless Apple is somehow able to successfully argue that Qualcomm owes it, in effect, rebates for royalties it paid in the past (i.e. from 2012-ish through 2016) because Qualcomm behaved improperly in forcing Apple to pay higher royalties than it should have.
There are two issues with regard to royalty payments which Apple has (effectively) withheld from Qualcomm. It withheld payments to offset the $1 billion in BCPA payments which Qualcomm withheld. But then it stopped paying royalties altogether when the BCPA expired. So Apple hasn't - the best I can tell, based on various court filings - been paying royalties over the last 2+ years (in addition to having withheld some royalty payments from when the BCPA was still in effect).
During that time Apple would have used a lot of Intel modems for which patent exhaustion wouldn't be an issue. Intel hasn't been paying licensing fees to Qualcomm for the SEPs used in those modems because, as I'm sure you know, Qualcomm has long refused to license its SEPs to Intel. (Presumably that will be changing as Judge Koh has now told Qualcomm it has to.) Who knows how long it will take to settle these Qualcomm-Apple issues. There may be 4 or 5 years worth of unpaid royalties owed to Qualcomm. Even at 5% of modem cost, that could be a couple billion dollars worth of royalties owed to Qualcomm. And, again, that would be in addition to the royalty payments withheld from when the BCPA was still in effect.
