Though there hasn't been much research on it, I suspect that methoxetamine (MXE) might have the same anti-depressant effects as ketamine. Also, it doesn't have the urinary tract issues.
Also, it's much much cheaper on the black market than ketamine. We're talking around 1000 (recreational) doses for $20. Compared to say 10 (recreational) doses of ketamine for maybe $50?