That is for Basic fares with the inherent limitations of that fare, though. The Extended Comfort seat selection cost is fare bundle dependent, so is going to be a lot more for Basic than for the Econo or EconoFlex fare. Probably cheaper to buy an Econo fare then upgrade to Extended Comfort than to buy Basic then upgrade.

I can’t see that they would provide any incentive price wise to purchase Basic then upgrade to Extended Comfort than upgrading from other fare classes, otherwise no one would tend to buy the other fare classes initially, if they did.