LOL here we go then i guess ;)
There are 531 plants.
Each plant will produce at max 4 ounces.
The average price per ounce (28.3 grams) of cannabis is £200.
200 times 4 is 800.
531(no. of plants) times £800(max profit from one plant) is 424800.
less than half a mil... So lets double the yield to 8 ounces from the plant instead of 4... (very unlikely but i guess maybe possible)
still less than one million pounds because 424800 X 2 = 849600
That's at price per ounce.
If you're selling like over even 3 ounces let alone 500 ounces at a time then the £ drops, as with anything in bulk.
Also, by the photos it looks as if he has around 10 plants per lamp. This will reduce the yield compared to 4 plants per lamp. (or less, as with any form of gardening, more space to light, the better the plant will grow). So i doubt he is getting more than 4 OZ from a plant.
No, i don't grow cannabis, and i could do this for any street drug from crack to xanax. So it proves nothing.
Anyhow... over 3 million is a massive exaggeration. Especially when you take into account the overheads for those lights.