I wasn't sure myself, so I did a little research: you can get 300 minutes (there's typically no difference between local and long distance minutes in the U.S.) and unlimited SMS and data on Virgin Mobile for $35/month (although they throttle your data after 2.5gb/month). That's about $10/month less than I'm paying right now - I'm on a shared minute plan which comes out to roughly the same amount, except my data never gets throttled. In addition, the phones available on prepaid plans typically aren't subsidized at all, so you'll be paying anywhere between $200-600 for a phone.
I just checked my data usage and I apparently average about 330mb/month. So, for me it might make sense to switch providers after my contract is over, but we'll see how my data/calling usage changes over time.
But I got off topic and didn't really answer your question: looking at http://www.pcmag.com/article2/0,2817,2375644,00.asp, most plans are going to be around $30 for 1000 minutes and 1000 sms, although a lot of the plans either have very little data included or have high prices if you want more data. I didn't realize you could customize your cell phone plan this much - if you only use two of the three (calling, texting, data), you can get a pretty cheap prepaid deal.