You have to define "inexpensive", but if you mean under $800 new, then the answer is pretty much "No".
You can find lots of inexpensive 500mm f8 mirror lenses which can be mounted on an EOS body. They are fixed aperture and manual focus only, but you can find them priced from around $100 on up. The cheaper ones aren't spectacular quality, but they are cheap!
For example there's the
Opteka 500mm f/8 for $90.
Probably the cheapest AF 400mm lens for Canon would be a used Tamron 200-400 zoom. They sell on eBay for something like $200-$300. Not a bad lens.
Try this:
Search for Tamron 200-400 for Canon on eBay