Don't assume the Sock It is 65% -- if it doesn't say, it's probably not. They've been selling diluted blends, when they can.

5 liters of bleach => abt 0.4lb chlorine, or $4.88/lb
7kg trichlor (90%) => 13.9lb chlorine or $2.86/lb

HTH ???

80,000 liter => 21,000 gallons => PF = 6.

350g TC is about right; didn't check the others. Sorry about converting SI to US, but I've done US so long that I can check those calcs in my head, whereas I have to put SI on paper to make sure I'm doing it correctly.

Keep in mind, when you use the pucks your CYA is going to rise 2.4 ppm when you add 4 ppm FC with trichlor! That will get to be an issue eventually. You may want to look at a SWCG, which you can use in conjunction with tabs. Using some tabs will keep your pH down (SWCG's tend to make it rise) and maintain your CYA, but using the SWCG as primary source will be relatively inexpensive (over the 4 -6 life of the cell) and won't cause CYA rise.