Sure, they lose the mechbay money, but that's about it since very few people would buy a cbill version of a mech just to get it 2 weeks before it is available for in-game money.
On the other hand, a whole bunch of people just got a Thunderbolt. Now, they'll probably want to fully level it, which requires 3 Thunderbolts total. That means they may end up needing a spare mech bay - or two - for the extras until they get them all leveled and then decide which ones to keep.
Long story short, i suspect they aren't losing as much money as one might think with these mech give aways.
Edited by oldradagast, 22 April 2014 - 12:11 PM.