Wow - $10 A LITRE!?!?!?!
I get mine from my local Asda for about £4 - £5 for a 5 litre container, which is a lot, lot cheaper. It's worth shopping around if you don't have a bigger supermarket close by, although some of the smaller shops and garages sell it as ironing water, or car battery top up water, at a much cheaper price than you are currently paying.
I think you may have overlooked the essence of the message you responded to. His point was that there's a difference between distilled and de-ionized or demineralized water. I think everywhere in Europe it's fairly simple to find de-ionized or demineralized water for about €0.50/ltr in a local supermarket, DIY store etc. Confusingly, some of these stores sell de-ionized water as distilled water, while it's rather unlikely that it's actually distilled given the price point. I just did a quick search and the only place I could find that sells
distilled water in my country asks around €4/ltr for it.
Of course, for amateur photo chemistry, in 95% of the applications, plain tap water is perfectly fine (I'd say 99% if your tap water is halfway decent, but we're not all that fortunate). Of the remaining 5%, 99.8% of the applications will do fine with either demineralized, deionized or distilled water. The virtually negligible remainder actually requires distilled water - and then we're talking about applications such as pretty advanced emulsion making.
So for all intents or purposes, either tap water or demi water are just fine.
The recipes calling for 'distilled' water are in virtually all cases over-specifying for no apparent reason other than lack of awareness.