I don't know if this could be useful to anyone for their MS, but, one might want to look at tiomobilepay versus Plastiq when it comes to cost.
$2.99 for $350 (or 3.99 for 500) at tiopay versus 2.5% at plastiq.
I do not know if they do accept CT, but, for roughly a cost of 0.35% it seems one could MS. (0.85% cost - 0.5% reward from CT and earn miles/points in the process). Anyway, just for the MSers out there... If this works, I have not checked (nor will).