I'd pay the original retail price on mini + shipping and no more.
Same for a quad.
Ha ha ha. It's like half the people on this forum are slightly 'touched' when it comes to mining. Look at Dash profitability before making joke-offers. Dash price is down 50% since absolute peak, but diff is also down 40% so a single A-900 still makes $1000/month drawing $50 worth of power, and your suggestion is the seller sell it to you at 2 months ROI..
You clearly don't actually own an A-900, do you even mine?
We can all enter numbers into a calculator. But if you believe the numbers are exact you're dumb...
1. Don't be dumb
2. Be lucky
On a side note...what he wants for these would buy you more passive income if you bought the equivalent value in pretty much any other type of asic.