From what I've seen, they're usually not even keeping the Seiko dial. They're just slapping a Seiko logo on a fake Rolex/AP/Patek dial.
They may be cheaper than a Marinemaster, but those movements themselves are cheap. I've heard before that a lot of the ETA/Selita/Seiko movements that these "cheaper luxury" watch manufacturers use can be had for $8-$20 on Ebay.
My personal opinion - these types of mods are better when they exhibit a great deal of uniqueness, so that they maybe share similarities to the homage target but aren't a direct copy. Rather than wearing this:
and having someone from a distance get all excited to take a look at your Hulk, only to be told it's a fake Rolex case with a Seiko logo slapped on it, I find more appeal in this:
Where it's not going to be confused for any popular watch but could serve as conversation starter and really is more of a unique modification.