What's the best way to get unused, urban outfitters style clothing at somewhere around Old Navy prices?
Urban outfitters is still dirt cheap. As others have said h&m, eBay, and thrifting are all.. Cheap. Could also try Zara but that's not quite as "hipster" as you want. Uniqlo but that might be too expensive.
UO is cheap as hell if you go to the sales section when they're having those 40+% sales, sometimes even without the sales they're still super cheap. don't go for all the stuff that gets put out in the front of the store when it'll be at the back in a couple months, if you're that cheap you can handle waiting. H&M is also cheap in the sales racks, and their non-sale stuff is... hit or miss, really. Cotton On is also decent for their prices, sale section again. I actually managed to cop a really nice black bomber from CO a couple years back from the sale section for $20, now it's starting to get a sick fade on the dye because it's relatively cheap stuff, not to mention the fit is great for me.