https://www.daqua.co.uk/reverseosmosis.htm
The price of these have gone through the roof:
Axeon £296.00 (£356.00 including vat and delivery)
I agree that Axeon membranes have got more expensive, but the HF5 is the only truly low pressure membrane available. The current US$ exchange rate hasn't helped.
In August this year (2022) my HF5 membrane will be 10 years old and still producing water at a rejection rate of 97%. I'm not complaining about the cost of that.
Our water pressure is between 50 and 55psi and our water is around 125ppm. I've seen it as low as 97 once and as high as 150ppm. My r/o produces 2lpm of pure to slightly more waste (about 45 pure to 55 waste.)
A 25litre bag of resin lasts me 4 years.
I could have purchased a cheaper Chinese made membrane, but I believe that in the long term it wouldn't have lasted as long, and I would have used more resin polishing the pure off. Remember the cheap 4040 membranes WCW were selling? They even listed the rejection rate at around 80%. Yes, we would save money on the initial purchase price but the cost of resin polishing the pure off would have negated that very quickly.
I seem to remember that Daqua used to sell the Champ membrane housing, which was much more expensive than the current stainless steel housing. Using the cheaper alternative would help to reduce the overall cost of a 4040.