Yes, before 0930 when the fare is set by CrossCountry (XC) is generally not going to be valid on an Off Peak ticket, so you're looking at £229.20 for an Anytime Return (
SOR), or an eye-watering price not far short of that for some expensive through Advance fares.
This is because XC want to charge a premium for longer distance passengers at a
much higher price than many short distance passengers would pay to occupy the same space.
However you may be interested to learn that a forum member has created a booking engine -
Trainsplit - that will sell a combination of tickets at the best price it can find (this is not guaranteed to be the cheapest, though it often will be).
In this case it will sell you tickets at £109.62 (each) if you depart, at 0649 and return at 1850, simply choose your desired times and the site will do the rest.