Why is it that for some people everything has to be a 'con job' or a 'rip off'? Toilet fluid is like aftershave, if you like the smell and you like using it, you buy it it. If you don't like using it you don't have to buy it, no one is forcing you, it's as simple as that.
How can anyone be trying to con you? Personally, I've tried all these quack treatments and none of them work for me as well as toilet fluid and I much prefer the perfumed smell of it to the horrible smell of using nothing. And if you use nothing, when you come to empty it the smell is revolting.
I buy five litres of my local dealer's own-brand for about a tenner and just put 100mm in, as we empty it whenever we get the chance, so it lasts me for months. It's the old story I'm afraid and is nothing to do with the environment or the scent of toilet fluid, it's all about the cost. If you don't want to buy toilet fluid, that's fine, it's a free country and I respect your choice, whatever reason you have, but please don't suggest that those of us who do prefer it are some kind of idiots who don't know when we're falling for a 'confidence trick'! We use it because we like it and we find it the best solution, and some of us have also caravanned and motorhomed for decades.