I'd think these tools still necessitate new investment in cost, implementation and training for many TMCs, and especially for agents used to faster command-line entries, NDC bookings will reduce productivity. The "penalty" then is for increased time and cost that the TMC does not incur for carriers marketing their entire fare offering through the GDS. GDSs and any additional software/tools utilized are all agency costs, so it's unclear what's meant by "lost GDS revenue".