Yes agreed, from whats been shown so far, the D5 seems a better buy.
But therein lies the weird part, as far as I know, Sabaj is connected with SMSL but their products don't seem to be sold within China, unlike SMSL. You can't find Sabaj products on Taobao or JD.com.
That said, I fully expect the M500 prices to taper towards US$350/- in 2~3 months. Possibly lower when the 11 November sales come around.