^^^ 800$ is ridiculous, I think. Check around.
However, 800$ is not ridiculous IF it goes internally as well, which you can't tell from the picture. As weird as it sounds, grab it- and see if it seems removed from actual tissue (so you can seem to grab it under the skin and move it around without it seeming really stuck in place). ... This is assuming its not painful... Of course.
The thing that bugs me most about it is that it's irregular, which makes itself more consistent to be cancerous, and no benign. (Not to scare you, but there's a lot you can't tell from pictures- just that it is worth looking at)
Definitely get a couple opinions.. And ASK QUESTIONS ... See what exactly they are talking about doing to the dog, and why. See if what they are talking about doing is REALLY necessary.