If they've already invested $10.5Bn, that money is gone (especially if WeWork fails). If they truly think they will get $8Bn worth for investing 4-5Bn now, it'

If they've already invested $10.5Bn, that money is gone (especially if WeWork fails). If they truly think they will get $8Bn worth for investing 4-5Bn now, it's a rational choice. Adding your past investments to the tally is an instance of the sunk cost fallacy.