It's a tough call, because IMO your "Prescient Scroll" basically makes normal scrolls obsolete. My kneejerk response is that having them be only twice as expensive is a little low. From an absolute perspective, however, maybe it's just that normal scrolls are overpriced.
If you're looking to avoid broken-ness, your test case needs to be the Artificer. It has Metamagic Spell Completion, encourages UMD optimization and various infusions that could cause issues. Increasing the time to actually cast the spell--maybe make it 1 round, like a summoning spell--should remove most in combat issues.
Anyspell is not a good comparison I'm afraid, because it explicitly must be prepared in a domain slot. You can't make scrolls of it at all.
One of the most compelling purposes of scrolls in the metagame is to have access to spells you wouldn't be likely to need every day, but when you need them you can't afford to wait a day. Your system accomplishes this much more efficiently, so you would only need a handful of prescient scrolls to accomplish it.
(On a totally unrelated note, maybe come up with a different name to avoid linguistic confusion? Just a thought.)