Re: "ethical" behaviour.
New business case proposal:
1. Buy zero day exploit for $x
2. Sell zero day exploit for $x/10 to 11 customers (i.e. knock-down price)
3. Expose zero day through puppet company to reduce value to zero.
You make 10% to cover your running costs and you eventually eliminate all known exploits (or people stop buying them).
Worth a go?