I don't know if anyone else has noticed this, but although the cost per spy seems to be at on a fixed ascending scale, any extra paid over the cost of this spy is lost, nad no matter how much you spend, you cannot train more than one spy at once. This became clear to me when about 7500 on one turn 8000 on the next and only got one spy, while the next turn I was able to train the next spy for 8000.
We really need cost overpayments to apply to the next spy or be returned to the treasury, or at least a price to train next agent counter.
Scincerely,
Scintor