So, in my example, the cost of the card is 0, it's modified by infamy tokens to be 2, and modified by another card/event to cost 2 less (-2). What you're saying is that they all have their effect at the same time, right?
0 + 2 - 2 = 0, or 0 - 2 + 2 = 0
That's good news. I was fearing that, if something reduced the cost, this reduction would have it's effect first, before the

effect, resulting in...
0 - 2 = 0 (because you don't go below 0), followed by that result +2 = 2.
But I see by your example that you don't raise negative numbers to zero until after everything has been accounted for and the captain goes to "pay" for the card.
