The Samsung Galaxy S3 and other flagship Android phones are not cheap in China or in other parts of the world. The cheap Android phones are made by those Chinese companies that make those ultra-cheap $40-70 tablets we see.
Apple's marketshare is small in China, but its revenue and profits is large.
That 90% Android market share is like silver jewellery, more of it is being sold, at cheaper prices with small margins. Apple is like Platinum jewellery, less being sold, at higher prices and higher margins. Other flagship Android phones (S3) are like Gold/Platinum jewellery.
PC market accounts for 90% of sales, within this 90% are many manufacturers, Dell, HP, Acer, Asus, Lenovo, Sony, Samsung, etc. Each one of these companies really represents 10% of the entire market (for example), which is the same as Apple claiming the remaining 10% of the 90%, it as a computer company is making just as much money as a single PC firm, but obviously not as much as all the PC firms (the 90% marketshare)