I never had to replace a battery on an Apple Device.
Although I know if you do then, it cost $100 and you will generally get either the exact same device or an upgraded version.
The reason they have less of a share of the market is because of price.
Where they do have lower prices like mobile phones. They have a large market.
What is most important is Market cap. Overall Apple has a larger Market Cap than Microsoft. Apple leads while everyone else copies and sell cheaper versions.
http://finance.yahoo.com/q?s=AAPL
and
http://finance.yahoo.com/q?uhb=uhb2&fr=uh3_finance_vert_gs&type=2button&s=MSFT%2C
AAPL has a larger market cap that all but one or two companies in the world, not just MS.