Actually, going back to the old Transports costing 8 would probably favour the allies massivly.
The old transports had a 1 in combat and was a hitpoint to take as casuality.
Lets take US as an example. If they where to make a fleet with 8 transports to threathen to land in europe. With transports costing 7, they have to use about 56 IPC for the transports. They will probably need about 4 other transports as well, so in total, they pay about 82 IPC for the pleasure. If transports cost 8, they pay 96 IPC. So where is the gain? Well, the gain is that they can now reduce the number of DDs needed to stand against luftwaffe. If we assume that 8 TTs is with the main fleet, then they would need about 5-6 fewer DDs in the main fleet. If we say they need 4 DDs less (then, they have the same number of combat dice in the main fleet, but with 4 extra HP), then they save 32 IPC in DDs. So buying TTs at 8 with 1 hp and 1 Combatdie will make the us invastionfleet at least 16 IPCs cheaper, probably more in the range of 24 to 30 IPCs cheaper.
The point to making transport cheaper would also be to help out Germany with Sea Lion, as it nearly always proves to be too costly of an operation.