>>149455086A large part of it is that American comic page counts tend to be smaller, even in OGNs you're really planning aroudn that hard page number. Those extended sequences in manga come from being installments with no set ending expected. I'm sure many cases it's to give some breathing room to write plot, but fans like it.
If you need to make a battle/game take place for multiple chapters,you have way more leeway.
Plus I think expectations for American comics tend to be for more story- and price probably has a part of that too. Manga is just cheaper overall than comics by a large margin. Big 500 page shonen jump books are barely $3. There's factors for that ofc, cheaper paper, no color, but the biggest will always be that they just plain sell so much they can sell for less and break even and then some.
You pay $3 for a SJ chapter light on plot to be a long fight sequence, and you still have other things to read, and it wasn't much of an expense anyway.
If you pay $5 for an American comic and just get minimal story and you can read it in a few minutes, it feels like it was overpriced.