Cheap, but reliable. And fast. It’s also easy to do, easy as driving a nail.
This is an old trick that I learned from my time doing concrete formwork, basically you drill a hole just a bit smaller than the width of two nails, then drive the nails in. Normally, for two common wire 2″ nails you would drill a 3/16″ hole.

2″ nails would be used to attach stock that’s 3/4″ or less. To attach stock up to 1-1/2″ thick, 2-1/2″ nails are used in a 3/16″ hole. These hold remarkably well, better in fact than the powder actuated fasteners (which will often blow out the surface of the concrete) and nearly as well as actual concrete screws.

I’m using 2″ galvanized ardox (spiral) nails, which are a bit thinner than common wire nails, but both work the same:

Occasionally, they may bend over, but there still enough holding power:

A couple of cautions about this method: it works best in poured concrete and concrete block. Clay brick or lightweight concrete block are not usually suitable. Although this is a very strong method for attaching wood to concrete, like all other methods, it is not 100% guaranteed not to fail.

I’ll mention that there is another very similar method that uses a regular wood screw and a piece of copper wire (usually #14 house wire). The procedure is the same: drill the hole, slip the piece of wire in so that it bottoms out in the hole and drive the screw in. If the wood screw is of good quality, this will be as strong a connection as a real concrete screw.