Here's what I did: I looked at the Wealth by Level table, and then tried to match the price of the item for the percentage of wealth the item would be for certain benchmark levels.
For example, Item X might be the big magic item at level 6 (50% of wealth by level), a major item at level 9 (25% of wealth by level), and a cool but useful trinket at level 12 (5% or 10% of wealth by level).
It's not an exact science, but it's a good guideline. Also, it helps if the big magic item level is the minimum level for that item. Then a crafter could invest time, money, and talent (Item Creation Feat, necessary skill ranks or spell knowledge, etc.) to make it at that level.
I think that wondrous items are amongst the hardest to price but the best guidelines are probably these:
http://www.d20pfsrd.com/magic-items#TOC-Magic-Item-Gold-Piece-Values
Probably not. But some items are not based on spells or mathmatical formulas. And some of those formulas make no sense. This is more of a ballpark method.
Or the neighborhood near the ballpark...
Don't do it that way. Listen to the RPG Superstar panel discussion where we talk about price. Bottom line: you don't actually have to get it right, just don't get it wrong. We dont have time to check item pricing. Our review is more gestalt than that--we take the price of your item, put it into the price list of wondrous items, see what is right above it and below it and if that seems about right then its fine. But if it seems out of whack, then we look closer at pricing.