The Court of Appeal have confirmed the case of Elsayed  EWCA Crim. 333: the value ascribed to illegal drugs is essentially a fact driven exercise.
Faisal Osman appeared for the Prosecution. The appellant's appeal was refused.
R v Lister (Joe)  EWCA Crim 2290 (para. 12):
"In the written submissions, prepared by the previous advocate reliance was placed on the decision of the House of Lords in Islam  UKHL 30 as supporting the argument that the judge should not have assessed the value of the drugs at Elmhurst Close in the way that he did. The market value, it is suggested, is the illicit market value of the plants upon seizure. We disagree. This submission, with respect, confuses the valuation of benefit with the assessment of the available amount. Islam, as this court observed in Elsayed, involved an early interception by customs officers of imported drugs. The case was concerned with the question of whether drugs could have a market value, not for the purposes of deciding benefit but for the purposes of deciding the available amount, which is not the issue here. On a proper analysis it does not support the appellant's written submissions. As the Judicial Committee observed, and as was underlined by this court in Elsayed, (see in particular paragraph 25), while the market that has to be contemplated in assessing the available amount under section 9 of the 2002 Act must be taken as one to which the defendant can resort legally, when it comes to calculating the amount of his benefit the judge has to look to the market where such goods are ordinarily bought and sold. In the case of illegal drugs, as here, that market must be the market where the defendant will be expected to dispose of the drugs for profit and his benefit must be valued accordingly."