I did this install on my 04 back when we first got it, using a camera named "Savv RV5000". It is still working perfectly after 7 years. I don't know if these are still available now, but make sure whatever camera you pick has wide angle coverage, low light visibility, and of course water proof. The Savv has been perfect in these respects.
I did not have the monitor in mirror setup, but a couple of us (from old sinnnaclub.org) figured out how to hook it up to a Toyota navigation unit's screen. Power from splicing into the backup light socket, so it turns on automatically when shifted into reverse.
Yes $550 is way too much. If you are semi-handy, this is a very easy install.