I just received my 2nd reburb ZUMO 550 from Garmin in 2 years! I got this one back in less than 5 days from when I sent my defective one back in. No charge for either replacement, even though my original unit was waaayyy out of warranty.
Hmmm seems like I may have paid your share...lol I just recently had to send my 550 in and they took my credit card info before they would even give me the RA#. Mine, like yours was waaaay out of warranty. The normal out of warranty price is $150.00 for the exchange. Which is what I paid.
The do have Great service and other than the fact that it took money out of my pocket this is not a complaint.
Their return/replacement policy may have something to do with the particular problem. I think my issue has been identified as a recurring "bug" in their unit that they feel is a manufacturing defect. Not sure, but I have talked with a few other Zumo owners who experienced the exact same issues as me, and they got replacement units also.