Z9 Mini @ 650-overclock hovers around 14k and 370w-from-the-wall - shows +-$14/day on WhatToMine, now. If Batch-2 start shipping in 2 days... and say some Batch-2 owners paid about $800 ($850, minus $250 coupon, plus PSU, plus shipping = $800'ish)... could mean a 2-month ROI. Say 3 months with price-drops/diff-increases.

So Batch-2 Minis should easily pay for themselves by Christmas.