People started to get a clue about this 5-10 years ago though. It used to be much worse. I recall having to deal with it daily and I don't think about it much any more - more like a weekly exception.
In fact, now also I get some places trying to be too helpful to the point of being confusing. For example, a trainer store that auto-detects location and lists prices in GBP but sizes in US (without indication) and doesn't actually have an EU/UK distribution centre. So whoops it's going to take ages to arrive, it gets re-listed in USD at the final checkout, whoops again, 3% charge from my credit card, and then the wrong size arrives. But at least I knew the rough GBP amount!
In fact, now also I get some places trying to be too helpful to the point of being confusing. For example, a trainer store that auto-detects location and lists prices in GBP but sizes in US (without indication) and doesn't actually have an EU/UK distribution centre. So whoops it's going to take ages to arrive, it gets re-listed in USD at the final checkout, whoops again, 3% charge from my credit card, and then the wrong size arrives. But at least I knew the rough GBP amount!