Fedex will continue to charge as much as they can to boost their profits. This move will increase their profits, making $1.50 on each of 100 million deliveries instead of $1, boosting profits from $100m to $150m
However if they were to undercut UPS and others they might be able snap up UPS business, dropping the profit to $1, but on 200 million deliveries, and thus they'll make $200m instead, you the customer will have a cheaper delivery, and everybody wins
They're not really competing on price but on quality. They make the most money with super urgent deliveries. If they offer later pick up times or earlier guaranteed deliveries, customers will be happy to pay more. And their IT system is crucial for that.
However if they were to undercut UPS and others they might be able snap up UPS business, dropping the profit to $1, but on 200 million deliveries, and thus they'll make $200m instead, you the customer will have a cheaper delivery, and everybody wins