When buying scrolls for higher level campaign play do you use the lowest cost possible i.e. a Scroll of Invisibility, Greater would be 525 G instead of 700 G because a Summoner can cast that spell as a 3rd level?
For home games, it's based on whoever actually made the scroll, not who could. So, if you bought one off of a Summoner with scribe scroll, you pay Summoner price.
For Pathfinder Society, scrolls are always assumed to be made by Wizards or Clerics, where those spells are on their lists.