The 5D is a great camera and there is now doubt is probably a better body than the T3, though the T3 has received good marks for it's image quality. Unless you know the provenance of the 5D then you are essentially buying a pig in a poke. The 5D has a reputation for having problems with the reflex mirror falling off and a tendency to have the sensor get dirty, hard to clean, and easily scratched. Not to mention it's sensitivity to humidity causing the camera electronics to fail pre-maturely, not to mention the weird color problems with the LCD.
All things said I would purchase a 5D over the T3 if I could get at least a 90 day warranty on defects and purchase it for $K or less. KEH.com lists the 5D @$1299 which I think maybe reasonable since the camera has an EX rating. However for $700 more you can purchase a refurbbed 5DMKII directly from Canon.
Sorry I missed your figures in the subject title.