Opportunity cost... they're forgoing potentially millions of dollars* in future revenue in an attempt to boost employee morale. Sounds like they're also offering that gift to some of those who have already left the company this year too, which they really didn't have to do.

*Note: Not a hyperbole. Napkin math: assume 50K employees use it and let's say that the average round-trip ticket price cost $300 - that's already $15 million.