Finally, after weeks of wanting to do this, I got the materials and time. Outdoor carpet was 50% off because it was dusty and creased, neither of which bothers me in the least given how it'll be abused, around $6. Strips of wood about $3, nails $2.50. So all said and done, I've got maybe $40 in it. I probably could have spent a little less, but what the heck, I've got it how I want it, and you can't put a dollar amount on that.