Depends on buyer. And condition!
Asking is not the same as sold for , so don't base a value on someone else's asking..
Per this link the seller is around a grand high.
For Sale on 1stDibs - Stunning and very rare, this high style Art Deco mirror features a pair of deer under a spreading tree, all alive with a silvery shimmer that is entrancing.
View this item and discover similar for sale at 1stDibs - Seldom seen Art Deco black glass mirror (vitrolite), circa 1930s, beautifully reversed decorated with wonderful flowering tree and deer motif. Retain original