I think I'm most concerned with purity over price. Who seems to be selling the most pure product these days? It's been almost a year since I've last purchased. Seems like shops come and go with pretty high frequency.
I used Southern Research Co. for a while and really loved their stuff.
It's indeed tough to keep a finger on the pulse. I haven't seen any outstanding independent lab tests as of late. Consider the ARR offering a do not sell price, not an indication of a stellar batch.
Fortunately 99 out of 100 suppliers offer high quality/purity peptides, mt-2 in particular (as it is generally a top seller). Sellers I try and avoid are the ones offering complex polypeptide hormones you know are fraudulent given the price/scale.
I have not purchased from these guys before but based on all of the feedback to this question I can assume that they are reputable. I might even give them a try.