My bill is generally less than half of $100/mo and my phone was significantly less than $1,000. I also use Wi-Fi the majority of the time and still find my phone generally useful in areas where I don't service. Although admittedly, loss of service is a rarity for me.
Of course when you word it that way :) I don't spend money on a phone for the purpose of paying a bill. I spend money on a phone and pay my monthly phone bill because I think it adds enough value to my life to make it worthwhile. Others may make a different decision on the tradeoffs and decide it's not worth it. I was just pointing out that the numbers used in your previous comment seemed very high to me.
I've got two landlines at home. I usually have one if not two tablets in my backpack. Skype is my "mobile" phone plan and works wherever there is WiFi.