Originally Posted by
Spec1alk
I am curious if it makes sense to purchase a ticket in Main, then allow my PM upgrade for comfort+ to go through and then upgrade to FC. Or if it is better to just purchase FC when booking?
Nine times out of ten, it will be cheaper to just buy F.
As mentioned, if you really care, you can fish for the offer and change the ticket to F if it's not favorable. The most common case is that the buyup on a nonstop flight is exactly 7.5% more than the fare difference - most of the rest of the time it's even more than that.