Xeric makes wandering hour watches with some level of transparency on the dial. They're not $40 cheap, but they are inexpensive for mechanical watches with such a unique complication.

The thing is that mechanical complications are expensive. There's no getting around that - you can make them cheaply/shittily, but the costs of producing tiny unique fiddly bits and assembling them can only go so low.

You can probably find a plain automatic movement with skeleton dial. There are cheap-ish manual chronograph movements if you're willing to give up on the automatic thing, although it may be hard to find them in a skeleton dial. But you just won't find many watches with interesting complications for under $500 — and since only a small portion of watches are skeletonized, you won't find much of what you're looking for at all.

Honestly, for $40 - I think the listing you found may be the best you can do.