In the spring of 2012, I had USB ports on both a 5D Mark II and a 7D fail within a couple of months of each other. I would attach these after a day of shooting to transfer pictures. I never shot tethered. I looked back to see what the repair costs would have been, but both of mine were under warranty and they didn't list a price, just $0.00. I used a 60D in the same way at the same time and never had an issue with it.
One of the Canon techs even went as far as to suggest that it was common for people shooting tethered to trip over the USB cable and break the port. He then went on to ask if I had been shooting tethered. I hadn't and resented the insinuation. In fact the camera was placed carefully on my desk with a short cable connecting to the USB port on my monitor. I personally believe that the USB ports were defective on my 5D and 7D from the start, possibly bad solder joints that cracked after multiple insertions and removals or something along those lines.
I don't believe there was an issue with the USB port on the computer as it is still in use and and I have never had trouble with any of my other devices such as card readers, memory sticks and external hard drives.
I no longer transfer pictures via USB. I now pull the memory cards and use a reader. I don't want to go through another failed USB port on one of my EOS cameras.
I know that doesn't help you as you need to tether, but wanted to share my experience. I was hoping that one of my invoices had a price. Good luck!
So I shoot most of my work tethered to a laptop. Unfortunately the usb connector on the camera has gotten loose, it still works fine if the camera is steady on a tripod and not moving at all. But for situations where I like to move the camera a bit around in between shots i often loose my connections.
My options as I see it is.
1) Get it repaired, does anyone know what this costs? and time. I am based on the Canadian west coast if that makes any difference.
2) Get the wifi grip, i can then tether with wifi, or its built in usb or ethernet ports, correct?. Currently watching a few on ebay to see what they go for.
3) buy used mk2 or new 6d. Will have to hold back on this purchase till end of january. my mk2 does have around 110000 clicks so it is getting old.
If you have any knowledge, advice or thoughts regarding my situation it would be much appreciated.