In my opinion the prices have risen in London in particular because of the high rise on small grow-ops producing a couple of ozs of quality grade and charging 200-250 an oz, (partially to do with the contaminated products over the years and increased energy costs) I just picked up a 1.1g for £20, my last pick up ever at that price. The major problem is greed, it effects all of us and when the majority of growers sell for that price range, what is to stop the decent minded growers from charging a similar price? All the grower and dealers are really doing is shafting the consumer at the end of the line and either forcing people away from smoking or increasing the UK grow scene.
Its like the sub-prime housing market in UK, people are willing to pay more and more.... up to a point.