The Greek Medium Tank outranges every other tank with its cannon.
Also, the Mammoth would start regenerating once its under 50% hitpoints.
Am I saying two French LTs can destroy a Mammoth Tank in a 1 vs 2 battle? Certainly not, because the Mammoth would destroy one of the LTs which would cause a damage falloff on the Allied side.
On the other side, you need to pay 1530$ for one slow-moving tank with the same 600 hitpoints and a DPF of 1,00. For 1400$ you get two fast-moving LTs with the equivalent of 600 hitpoints and an accumulated DPF of 1,38.
This can be explained with a simple example: Compare two French Light Tanks with one Russian Mammoth Tank.
The French bonus has the biggest impact in the effeciency rating overall.
According to this analysis, the French Light Tank offers the best performance for its price.
The bigger the tank, the less cost efficient it is.