I know, old thread and all, but I just replaced my cracked glass. I broke it in November, it was from a corner-on drop from maybe 4ft above concrete. It still worked so I just lived with it for a few months with a bit of tape to make sure the shards don't fall out. Because I wasn't sure of my finances at the time as December to Feb. are usually slow months for me, I didn't want to spend a couple hundred that I thought it would take to fix it.
I paid US$30 on ebay, which included the glass, touch screen digitizer, two plastic spudgers and shipping from a domestic seller. You can buy just the glass face, but it's hard to tell whether the digitizer is damaged without disassembly, and it looks hard to separate and glue together well, I don't think it's worth cheaping out like that.
Add a razor blade, a hot air blower (intense auto shop version of a hair dryer) and maybe half an hour and it's replaced. It's not for the faint of heart, so it's probably best to get it replaced professionally if you're not into intense DIY work. The third party services I found started at $150. I don't blame them for charging that, I probably would too.
I didn't have a case for it at the time, which probably would have prevented all this. The previous case tore apart and I didn't like any that were on the market at the time, but that was a mistake. I should have at least gotten any ugly silicone case available to pass the time until better cases were made available.