Last time we personally bought saffron was in Istanbul ages ago , we plan on returning next year . Our guide helped us choose as we had no idea , language issues too . Before that was likely from Marrakech , more like 20 years ago . Before that was probably in France or Spain too ..
Then our friends also / usually bought / gave us .. frightfully pricey .
Assuming the more expensive it is , the better the quality . Sorry not much help here .