Yes they are available at between £1.50 & £3.00 per pack.
the issues I have with them are :
Portion / bag size is 250g
Calories per portion / bag is around 200.
So for an equivalent meal to a de-hydrated 800Kcal meal you need to buy 4 of them (and carry 1000g) as compared to 150g bag of de-hydrated food. Yes you can 'add something' to them but that is all weight carried.
Burning off much higher than normal calories hiking with a pack in hot weather needs additional calories to your normal intake.
When one 250Kcal meal weighs almost twice an 800Kcal meal I think the choice is easy.
My only issue with dehydrated camping meals is the price, if I could afford them then yeah, I would be right there with you! But I am looking at between £5-7 (pretty much my whole days food allowance) for a single meal from the local outdoor shops near me, which would be fine for an overnight or long weekend excursion, but for longer ventures (I am setting out on a 4 week camping trip this Wednesday) those prices are just not sustainable on my budget.
As for the weight, you are right they are much heavier, a packet of LWWF Chilli Con Carne and a packet of Pataks Rice for example weighs in at 500g and supplies just under 700kcal, but it only cost me £1.98 by comparison, and the rest of my days ration is typically made up of cheap, light weight, dried goods (porridge, powdered milk, noodles, couscous etc, with the odd chocolate bar or flapjack to make up the calories) and rarely costs more than £5. I may come across as cheap and stingy, but coming from a low income household I'm happy to suffer a couple of extra pounds on my back to save a few in my wallet.
Funnily enough I have been looking at food dehydrators on amazon recently, with the intention of trying my hand at dehydrating my own meals and snacks on the cheap. Anyone have any experience with this, are the commercial dehydrators any good?