If you look through the list, it is quite evident: the developer thought he is setting the base currency in his own (Ukrainian hryvnya), but it was, in reality, the USD price.
If I recall correctly, the Ukrainian translation of the Steam backend is still quite lacking, and despite popular belief, not all of them are fluent in Russian.

So, the usual?

It is simpler, the game is made by a Hong Kongese company, so the local reviewers upvoted it to hell. Kinda normal. The Japanese review sites also gave Biohazard: Umbrella Corps 65-85% all across the board, when the game ended up in the 15-45% range everywhere else.

Naturally.

Isn't it using one of the basic free engines? Dead simple Unity games can eat up a ton of system resources since newbie coders don't know how to optimise it properly.

Asking to leave feedback in some form is a normal for any content creator on any platform. Begging for reviews is okay, even begging for positive reviews. Offering something in exchange would be manipulation. But simple positive review begging is rather normal, for a time Artifex Mundi puts these in their Steam edition of the games as well (and begging screens for reviews have been common in casual games since around 2003-ish).

I also think you are jumping the gun here a bit. Steam games rely on user scores, so a little desperation is okay from a dev, as long as it is in the begging territory. Emotional manipulation may be considered manipulation, but considering how most Steam users are jaded bastards or ridiculously naive kids, I do not really think it is a particularly despicable practise, just desperate.

Isn't this the same Brazilian kid who was already discussed for the same behaviour once?
At any rate, he has his phone number in the games' support pages, so you can call and ask him the reason.

Also looks like a review-writing service. I thought those were dead ever since Valve had an algorithm that could find them occasionally and people can also report the very obvious low-effort ones.

For me, it works normally. I even get the You ignored this developer message if I open the games from links.

True, reviews look like the standard paid ones from the Original Curator group. But those users usually have more than one review posted or more games.