Wait and buy used is your best option if you want to go much lower than what you have. Overall, $103 is low enough off of the asking price that it wouldn't bother me to just take the plunge. Are there fake M50s floating around? If so, here is a very trustworthy shop for $110, it's the lowest reputable price I've found form a fairly quick search. They've been in business since before the internet, when you used to order stuff from companies in the back of magazines.
http://www.bhphotovideo.com/c/product/477843-REG/Audio_Technica_ATH_M50_ATH_M50_Professional_Closed_Back_Studio.html
Considering that minimum advertised price on them is $160 (aka, if you go somewhere like amazon, they will only be allowed to show you the price in cart), I'd be pretty happy at $110. For $90, you're going to have to wait for specific deals and be ready to pounce. For example, Beach Camera (one of B&H's main rivals, along with Adorama) recently had the ATH-ESW9 for $200. But this isn't something you can really count on. No one will be able to reliably say, "In 8 weeks, JR.com will be clearing out an excess inventory and will have an extra $20 off). Just yesterday, AKG K518 were $50 on Amazon, and today they're $80. You never know these things.
Cliffs notes: $90 is an unreasonable expectation to readily find these. Either wait and lurk all of the available avenues, or accept the currently-available prices.