I read somewhere that the number of Chinese cellphone users are about 450 million people. A cellphone costs in China about $30? (or maybe a bit less). Surely if you make $1 per day, you can't have that. Cellphones = a better indicator of middle class than anything else.
The average wage in China is actually $100 USD per month, or about $3 per day (tht's using 8 RMB to $1 ratio, which is now 7.7 RMB to $1 USD ratio) It's about 800 RMB per month, that figure though was about 5 years old.
In third world country people go in debt and deprive themselves from many amenities in order to have a cell phone a show it off. I think cell phone is the least indicator of a middle class. How about cars? How about nice and comfortable homes and apartments? How about PC and laptops? How about home internet and cable or dish? How about all the other electronics home devices and appliances? How about decent cloths? How about good food and the ability to go out a lot to eat in restaurants? How about decent healthcare? Those are real indictor of middle class not a cell phone! And based on your account, less us assume $ 100 month is what the average Chinese make, and if cell phone cost them $ 30 a month then that is 30% of their monthly salary, imagine how much less they can afford to other stuff with the remaining 70 dollars.
Cellphones became quite common in Zimbabwe in the last decade, because any attempt to string copper wire for telecommunications lines would only result in expanded employment for local jewelers. That's much of an indication of prosperity there, where the starving army has been shooting at Comrade Bob's palace in order to indicate displeasure about their limited [beans] diet.
Much the same is true in Southwest Asia, where distances or a shortage of wood for line poles make microwave and cell towers a more viable technology. If only people wouldn't use them for setting off IEDs and would quit shooting holes in their antennas.
Herat, Afghanistan cell tower link: