Yes, but it's not what Apple wants to do.
These lists count how many computers are sold. Whether the computer is £200 or £2,000 doesn't make a difference, it's one computer. The new Retina iMac starts at £1,999 ($2,499). Apple isn't going to sell gazillions of them. But someone else selling £200 computers must sell ten for every Retina iMac to make the same revenue.
Apple could easily build cheaper computers and sell lots of them. So what good would that do them? None at all.
The benefits of bringing more people into their ecosystem are obvious. Taking over education and corporate would be nice too.
And you're going to have to try REAL hard to convince me they could "easily" build a cheaper computer than the new entry-level Mac Mini. That thing is a total piece of junk. Truly one of the lousiest computers released in 2014. They cut so many damn corners with that thing, I don't know where else they could begin to cut? 2GB of ram maybe? Other than that, I don't see how they could make it any cheaper or crappier than it already is.
----------
Who cares about market share?
Pretty much everyone.
Only stock holders give two ***** about EBIT, profit-per-unit or other accounting metrics.