If it were not for the prospect of selling their shares to you (or back to Apple later), no one would have bought those shares in the first place. When a company is going through tough times, it can raise capital by issuing more shares. Apple is so successful at the moment that it does not need to do new public offerings, but it could choose to (like Nvidia recently -- not because of tough times, but because why not take free money when it's being shoveled at you).

Also, price is not based on market cap... market cap is based on share price and count. But the larger the market cap, the more money can be raised by selling shares without diluting existing shareholders too much.