So, the Quicken Rod is the only +4 rod in the SRD, and Ascendant Spell is the only +5 metamagic feat in the PF SRD.
While a quadratic regression (using the price as a function of spell level increase) gives a price of 54,900 for the minor, 106,000 for the normal, and 240,250 for the major, it goes without saying that math is merely a guideline for a base price, and that GM discretion is the best method for pricing a magic item.
So, what sounds like a good price for Metamagic Rods of Ascendant Spell?
Mitigating factors to consider:
Though the spell acts like its mythic version, it is not actually considered mythic unless the caster is mythic, so, for example, your Ascendant disintegrate is stopped by a 4th-tier caster's mythic globe of invulnerability, whereas a mythic disintegrate from an actual mythic character would not be stopped.
Even mythic casters cannot augment a spell modified by this rod.
Several spells have mythic versions that are completely useless to nonmythic characters (because all extra benefits are based on the caster's tier):
ablative barrier
animate dead
anticipate peril
antimagic field
grease
magic fang
murderous command
saving finale
sending
shield of faith
theft ward
time stop
touch injection
transformation
In addition, an even larger number of spells have very little additional benefit unless the caster has mythic tiers.
Reasons characters would want this rod anyway
The obvious (mythic version of many spells are more powerful than the nonmythic version even given the limitations of the feat and the tier dependency of many benefits).
It gives mythic characters a degree of flexibility, allowing them to effectively circumvent the restrictions on mythic spells known for a few times each day, albeit without the ability to augment them.
So, what are your suggestions? I feel of course that the Legendary Crafter mythic feat should be required to make the rod, but what would be a good price?