Modern vehicles make it worse because while once upon a time there were warnings that a battery was on its way out, modern vehicles often have ‘instant failures’ to start because of all the electronics trickling power 24x7.
You have described amoral capitalism where place and time utility are factored into prices. If ‘you’ did not need a battery ‘you’ would not be buying one so price is irrelevant. A real deal might entice you to put one on the shelf, but why since it is speculative?
When you need one you probably need it straightaway, thus the battery is in the right place at the right time, and that is high ‘value’ that can command a premium price. Have a flat battery? Shopping around costs money and time and possibly significant inconvenience while the vehicle will not start, not considering the possible need for substitute transportation.
Unfortunately there are many predatory operators out there, such as those you have called out.
A few years ago I had an instant failure and no alternative transport; the battery was 5+ years old so I rang RACV Battery Service (got a phone quote) where the installed price was surprisingly competitive. They came timely, checked the charging system, swapped the battery and took the old one for recycling. My experience was positive. The battery was still going well 5 years on when I changed cars.
