Pretty much. In my case, I am using Verizon right now, the cheapest plan you can get online is 450 minutes for $39.99 (disregard special deals etc), which is 8 cents a minute plus free nights and weekends. I called them up and they told me the lowest they can reduce my cost to is $30 for 300 minutes, or 10 cents a minute.
I rarely use my phone, by rare I am mean less than 300 minutes per month, including nights and weekends (but I like the convenience of able to call from anywhere I am, surfing, etc). Which means, even at prepaid cost of 10 cents a minutes, with no nights and weekends free, I am still paying less than $30 a month. Non prepaid plan would just be a waste of money for me.
Now if anyone knows a plan that's better than Amp'd for me, let me know
Oh, Amp'd is offering Motorola E815 for free right now with their prepaid plan, it's a very solid phone, no worth than almost anything Verizon has to offer.