On this year's trip to India (I go yearly with a non-profit), I ordered Verizon's Global Data Plan, so for $25 I got 100MB of data (at 3G or slower rates, granted). Since I was the primary blogger for the team, I passed the 100MB limit a few times, but that's only a $25 increment each time: without the plan, I believe it is $20.48/MB (emphasis there to catch your attention and warn you). After I got home, I turned the Global Data Plan off via their website.
Now, realize that that is Verizon's rate for India: they cover a hundred countries or so, but not Dubai, UAE, where we had a short layover on the way out and a long layover on the way home. On the first layover, I took my phone out of airplane mode, and blew about $50 in two or three minutes synching my email. Don't do this.
Phone and text messaging in India, even on the plan, were still way more expensive than in the US, but our team goes to back-of-beyond places, and we need to stay in touch, sometimes. Part of our team got scammed in a railway station, and I was able to get the phone-number of our regular tour guide to help them out and text it to my friend leading the other part of our group. (Under our tour guide's direction, he reported the incident to a policeman, and cancelled the credit card transactions he'd made under pressure, so it cost only time, not several hundred dollars.) Without a link to the web and phone/text access, we'd have lost a lot in that case.