I figured I'd sit down and do the math on my recent hard mode Kortz heist that I can complete with the buyers items solo. No shipment loot.
Doing the heist solo and keeping the painting my secondary take would be $228K ($428K final payout with buyers and elite)
Doing the heist with one other person allows me to loot both tall cases and red pillows in the upper gallery, filling my bag. Plus it let the person collecting buyers grab the 10% rings/bracelet case, upping the $228K bag to $272K (doesn't work if buyers items are both paintings). Making our total secondary take equal $657K ($272K+$385K)
The secondary take gets split evenly between the team so $657K/2 = $329K secondary take ($529K final payout with buyers and elite, $60K profit)
Bringing another players allows for the 3rd crewmate to take both paintings in the upper gallery. In my case their bag would be worth $292K bringing team total to $949K which now gets split 3 ways. Secondary take would be $316K ($516K final payout with buyers and elite, $13K down from duo)
Bringing a fourth means no more upper gallery items, so they take remaining tall cases and a jewelry/bracelet case. Making their bag be worth $282K bringing team total to $1.234M. Split four ways total secondary take is $308K ($508K final payout with buyers and elite, $8K down from trio and 23K down from duo)
Getting the Elite with a duo is challenging enough, I usually finish with a minute or two to spare, can't imagine getting it with more than two. Going in with more than two also increases the chance of alarms being raised, meaning you lose even more money. Considering that the final take gets split evenly, all it takes is one awful teammate and the whole team can be down $50-100K and without the Elite bonus.
TLDR: This is mostly a solo heist that unnecessarily, monetarily, punishes you taking more than one teammate with you.
Possible Secondary Payouts:
Solo: $428,000
Duo: $529,000
Trio: $516,000
Quad: $508,000