Good question.
I do not think anyone looking for a £70 half would look to pay £50 on a q of what they perceive to be the same thing.

Firstly, there is not one singular set "street price" for any one bud even in one city. Secondly, do not make the mistake of believing because a bud has the same strain name as another, it therefore has the same quality, nutrients, CO², cure, etc.

"This strain is £5 and that strain is £7" is not a holistic way to approach the market, there is too much variance and too many variables.