I have three sight pushers that ranged from a low of $75 to a high or over
$250. IMO, you get what you pay for.
The C clamp types are an attempt to save money (I like that approach) but
most that I've seen or used do more damage than I would want (probably
better than a punch and a hammer, but not by much).
Let's hope someone had a source for one that's worth having.
I think they work fine so long as the user is aware of its limitations when working with extremely tight fitting sights.
I have used such a set up to push front sights into my SR1911, but stop short when the outer edge of the sight base is about even with the plane of the slide and finish up at that point with a custom ground 1/4" chisel to fully seat it in the groove.