If we had more builders/owners in a more concentrated geographic area, a bulk buy of a few hundred kilos would make sense, but shipping internationally really builds expense. The low volume alibaba people want US$110 per kilo in small lots, no less expensive than Sintratec.
Agreed - the problem is when you want to experiment with different materials. It has been suggested that I go with a begging bowl to nearby, bigger sls businesses for a couple of kilos at a time. An alternative may also be Universities with 3D printing facilities. I'll see how I get on with the supplied powder first before getting too ahead of myself.