Prices have probably gone down in 4 days, deflation is pretty bad. :( Don't know what you lowered it to, but you should still be able to get 40-50M. Good luck. The 20M was definitely a low ball offer. As more and more Manticores are put on the market people will start looking for those 1100-1200 dps dex 2 socket versions. I'm watching prices for an upgrade but they haven't quite dropped enough yet for me.
It is not worth anywhere near 70m, I can get one with more dmg and a tad less crit for 40m. Anyway, I will offer you 35m for it. You would be doing me a favor because I won't have to go pay 40m and I'll be doing you a favor because I cut the tax. Go look at the AH, you can argue that my evaluation is off, but if you search the AH a little less strictly, you will see that I am right. What I mean by that is don't go search the top of your stats, rather, search at least 10 lower for every stat on the bow and you will see that there are bows out there with better dmg and a little worse stats for half of your asking price.