Aye the link tarbaby posted is very interesting, and should answer swiy's question fully.
is always surprised when he reads that link, that the end product is H4, like you'd find on the East Coast of the US.
Whereas H4 is near impossible to obtain, even in countries bordering Afghanistan, as since ~the early 1980's when Afghanistan began to become a major heroin
producing/exporting region, the final product, ready for both internal consumption and export to the rest of Europe, was H3, the base, smokeable form, requiring addition of an acid in order to dissolve, (unlike H4).
According to a UN report swim read quite a while back, the capability to produce H4 in Afghanistan and surrounding regions has existed for at least several years.
Yet still they skip a step and do it the 'old way'. Swim would have assumed that since they clearly have the knowledge and (I guess you could call it technology), to make relatively pure H4, they would have capitalised on that market.
However, swim supposes they still make billions as long as what is exported vaguely resembles heroin, -so perhaps, why make the effort, change the custom?