I think your leasing costs might be a tad light. 737Max8 are going for around $340,000 US/month.
The entire 777Partners’ (the number comes from their street address, not the plane, btw) various enterprises business models seems to be to sell at a loss every seat (plane, football stadium) and somehow make a profit on volume. I cannot even imagine how they could tart this portfolio of holdings up for an IPO.