While I definitely agree that saying it's upping the take home from 70% to 90% would be misleading - in a fair number of cases that 10% credit will be pretty easy to convert to direct value. It is certainly more valuable than, say, 10% of earnings being spendable on Amazon Basic items - they're not quite trying to pull a company store trick here and the fact that 80% of revenue is take-home sales already puts a decent chunk above Apple.
As a general labor rule, when a company gives me credit, I value that at $0. Even if this is technically wrong (it is definitely valued more) the reason for this is that the limitation imposed to how I use the value of my labor is a disingenuous negotiation tactic and I will not under any circumstances let my self by fooled by it. Therefore I treat the 10% credit as nothing more valuable then a smile or a letter of good will.
