Last year I built one. It's basically a sand-bag and a rear-rest that stops recoil.

It cost me about $7 to make the same thing...but I used sand bags that I previously had.

I put an adjustable front rest w/ a sand bag on it in front. Then I affixed an L-shaped piece of 1/4" steel to my shooting bench. I wrapped the steel w/ leather and a thin padding.

I shot a box of .308 Norma Mag shells from that rest last fall, and I was no worse for the wear. The nice thing is that the 1/4" steel flexes quite a bit, so between that, the padding, and the movement of the bench there is no danger of damaging the gun.

I just couldn't see paying $1-200 for a gun rest.