Treat a spell in a magic item that's modified by a metamagic feat as if the spell's spell level were actually higher
Magic Item Creation says, in part, that
While item creation costs are handled in detail below, note that normally the two primary factors are the caster level of the creator and the level of the spell or spells put into the item. A creator can create an item at a lower caster level than her own, but never lower than the minimum level needed to cast the needed spell. Using metamagic feats, a caster can place spells in items at a higher level than normal.
(Emphasis mine.) Certainly this rule could have used at least one example of its application right there, but we'll have to content ourselves with published examples that are close, like the major crown of blasting, a wondrous item that uses the 3rd-level spell searing light modified by the feat Maximize Spell (so occupying a 6th-level spell slot and mandating a minimum caster level of 11). While the major crown's text says it's made at caster level 17 (just like the D&D 3.5's similar major circlet), the major crown's math says—when the major crown's reverse-engineered—that the major crown's actually priced as if its caster level were 11, and that caster level 11 also conveniently jibes with the damage dealt by the crown's effect.
(Note that Pathfinder's antecedent Dungeons & Dragons 3.5—from which this rule comes—makes how to apply this rule clearer with, for example, its table of random wands that's also on Dungeon Master's Guide 246.)
So what Magic Item Creation means is, for example, when estimating the gp value of a typical continuous or use activated wondrous item when using Table: Estimating Magic Item Gold Piece Values, the game wants the estimated base price for the magic item to be the spell level modified by the metamagic feat × minimum caster level needed to cast that modified spell × 2,000 gp. Keep in mind, though, that few published magic items employ such modified spells, so getting the GM to approve such custom items may be a challenge.
Note: The GM—not the player or the PC—typically determines a magic item's gp value by first comparing it to existing items then the table. You might also be interested in this question.