Be interesting to price that up. I would guess the copper powder is expensive and the resin isn´t cheap. 5 litres cost me £227 with the club discount but excluding vat. Which raises an interesting question if I bought it through the marina would I have paid Italian VAT and how much would that have been.
Without trying to sound like I am justifying my decision or that I am biased in any. One of the reasons for a specialist resin is a controlled the rate of decay in the resin. I had read about people using this form of treatment and it basically not working, I understand this is because the resin encapsulates the copper. However I guess that if you ´scrape off’ regularly enough you will scrape the resin back and expose the copper.