Thats a pretty good price. On one AR I have a Tango Down model with the QD Swivel Slot on both sides, $75. It mounts on the buffer tube. No tube removable necessary. Midwest makes one that is a lot cheaper, $37 (see pic)
I never liked the Single point configuration, lack of Weapon control. But it works for some. I never carried an MP5 long enough to have an opinion but I would think Single point configuration had these smaller weapons in mind. Three point configuration just sucks, thats all I have to say about that.
I experimented with a lot of set ups. The best for me is a two point configuration. Both mounting points in toward the center, about 14" apart.
One point is attached to the TD QD Attachment on the Buffer tube. You can see the right side hole for a QD swivel in the M4 picture w/EOTEC.
The second point is attached about 14" forward on the left side of the KAC Rail. Using a MI QD Rail mount (See Pic of MI Mount) Next to the receiver. You cant see where it's attached in the M4 Picture.
This configuration works for me and my Rifle. You have to find what is best for you. Why didn't I mount one point on the Butt Stock instead of using a $40 to $75 Buffer Mount. Or one point on the Butt Stock, other point on the Buffer Mount...etc. You just have to find your sweet spot. My son is only 12 so we had to spread his AR Sling points out for better control (See pic, Tan AR) Either that or cut a $40 Sling