You are looking at a premium cabin flying through a fortress hub (EWR or IAD) at least 6 months out. That generally means someone with fixed dates and therefore no reason for UA to discount its fares yet.
UA is most certainly competing on the DUB-US route and on the Northeast - MCO route and it has sophisticated RM/IM software examining 100's of datapoints to which you do not have access.
Those likely show that as of now, people will likely purchase the more expensive fares so no need for UA to drop its fares. But, if UA is wrong, it can drop its fares and sell the cheaper fares later.
The real question is whether you wish to compete for those seats. If you want to lock them in now, you will pay the premium. If not, you can hope that they remain unsold and that the price drops.
Or better yet, fly the competition. That is what a smart consumer ought to do. Not as though the UA hard/soft product is so astounding on those two routes that you are seeing some intangible value.