Remove SD card from iMac CD drive
You can:


Get a piece of card / paper
Cut it out into an L-Shape and fold the _ of the L in half
Get somebody else to hold the computer up so that the CD drive is facing down
Put the piece of paper into the CD drive from the top and slowly, bring it down
When you reach the bottom of the drive, pull the paper out, gently and slowly.


The SD card should come out. You may have to do this a few times before it works - but it's better to try a few times than it is to pay Apple to fix this.