If I sell a call on AAPL $Apple (AAPL.US)$ at a strike $170 ...

If I sell a call on AAPL $Apple(AAPL.US)$ at a strike $170 and the price is $172, I'd receive about $2.50. Now, if AAPL soars to $200, I get to keep my $2.50 but then need to sell AAPL to the options holder for the agreed upon price of $170. So, i lose $30 because i have buy at the market price (assuming i hadn't already bought shares).