What's the explanation behind that?

To make it clear that even the most blatant of hacking won't get you banned.

Why are they telling people the prices?

To make them aware of either how much, or how little it costs?

Why are they telling exactly what you get for your money?

A combination of the two points before. To make people realize not every hack is a free ESP only that gets you banned in two days because its instant detected. To make them realize that the exact other end of the spectrum exists too.

Why is that relevant information at all if these people want to dissuade people from purchasing the cheats?

The goal isn't to dissuade people from purchasing cheats, it's to attempt to convince this sub, which has adopted a firm "There are no cheaters in Tarkov" stance, of the fact that there are, in fact, cheaters in Tarkov.