Bargain, £11.13 and you can sue them for $250mil!
Don't be taken in by the marketing blurb. Glysophate is glysophate. At more than 20 times cheaper, you can afford to spray it very generously.
True but Roundup is the leading brand. I imagine the ebay glyphosate you mention will be from a generic brand. Also, roundup also contains an adjuvant that disperses the product better to give a better coverage.
You can get 5 litres of glysophate concentrate for about £25 on ebay. Dilutes at 20ml per litre of water = 250 litres of weedkilling solution.
Happy shopper you beat me to it. For years people have been saying Roundup is carcegenic. Plenty of old household items are probably carcegenic, like asbestos, cigarettes, arsenic green wallpaper, talcum powder, mercury. There will always be done idiot like John Gummer who will feed a known danger to his daughter, saying it is harmless!