Well I tend to put 200g into a lunchtaker pot as a portion if I am just eating by itself or with fruit and in the berry or apricot flavours that is 1 syn.
So out of one sachet of mix you would get 5 or 6 x 200g portions I would say but to be honest I haven't worked it out properly because all of my family eat it.
Sporry that I can't be more helpful.To me the taste is important not nescessarily the cost