Posted By: 
AnonymousI've posted the technical reasons a few times but ran into this myself.  The very thin scanners use a different type of element for the scan, believe it is LCD or LED element.  They do great on flat items but have a very limited range of focus.
The thicker scanners with the older bulb type device have a wider range of focus and can do graded card holder much better.  
Price doesn't have a lot to do with it but the type of scanner does.
I ended up giving my thin scanner to my sister and buying another Canon for around the sam price, under $100.  Works great.
Adam B.