You didn't show the toggle, and it doesn't have the 'hump'. What makes you think it is a Mauser?
Prices are high for everything these days; I would have said maybe $900 but $1K is acceptable I guess...It may go fast, but for $1K I would expect a good bore (maybe some freckling but not a sewer pipe). Rough exterior is a minus, again a subjective valuation.
Barrel and sideplate look different than the rest of the pistol. Could be a plus.
I'm an older accumulator; if it looks as good in person as in pics I would jump on it. I like to enjoy my toys for a while.