I have two vices mounted on my bench, one is a Wilton 6" machinist vice for the serious stuff & I put brass sheets over the jaws or leather for dif things I don't want to mar. Got it at Lowes for ? $ 119. I think. Other vice is a Parrot Vice from Woodcrafts (green& $39.) and I put padded jaws on it, have the pivot piece under it that I got from Jerry Crawford (Holzum) I am pleased with it, BUT it is for light duty & not for clamping steel & etc. as it is just not make to do heavy work, as has been pointed out.
Have another parrot vice I slip off Jerry's mount & use for working knife blades, on & off in 5 seconds & back, works good for what I need it for.
On my other bench I use for really big stuff I have a huge Rigid or Wilton, can't remember which. But it is a hoss & must weigh over 100#. I bought it at a machine shop auction for $100 & it was a steal. Bought 3 others as well for the other shop. One like that would cost 5-700 bucks new I guess. Today, a cheap vice is not going to hold up to hard work or be precision, IMHO.
Keith Lisle