Cocaine in the US seems to stay the same price, and in many places it's the purity that goes down, but the price stays the same. I live in an area close to the gulf of Mexico where direct imports of cocaine are done,and also close enough to the border with Mexico,and the interstates going east and west and south to north that are both major trasit routes for cocaine,weed,crystal meth, etc.. Coke here is still pretty cheap and pure, due to the supply being high, and the demand being stable, or lower than in past decades becasue of many former coke users tunring to crystal meth as a cheaper , much,much longer lasting high. Coke sells for about $60-80 per gram for "flake" or "fishscale" as it;s sometimes called and an 1/8th Ounce (3.5 grams) sells for $80-150 each, the purity is the same or even better for the cheaper coke, becasue I can get it from higher level dealers who sell it cheaper, but at higher volume. purity is said to be from 70-80% for grams and so on..
I did coke in the mid 1990's that was much more expensive and was more around 50% pure and It was really shit IMO. I do not see how someone could get high off 4 or 5 % pure coke, I would think that all the cuts would clog up the nose and prevent what little coke is in it from being absorbed into the nasal membranes for the most part.
Anyway, big dealers could obtain some ammonia and ether and prepare base cocaine, which is up to 95%+ pure and then add hydrochloric acid to the filtered solution to get back cocaine Hcl, although at 5% pure, a 100 grams would give you only 5 grams of pure cocaine, 95-99% pure that is..But surely dealers who obtain mulitple kilograms of coke get it at higher than 5% pure, I imagine 50% pure for kilograms, although I dunno, but they could do and acid/base extraction and recrytalization with Hcl acid to obtain a very pure product, although, I imagine as long as people will continue to buy 5% pure coke, they will keep selling it at that purity..