I already have the black material cut to size and hemmed. I also have the Velcro. I tried hand sewing the velcro in place but the thread would get all tangled up and knotted. I'll look into taking it to a seam-person. (have to be politically correct you know)
As far as the cost, I didn't keep a running total. Three or four bucks each for the buckets and lids. The wood was from an earlier attempt at a riser. When I got a subscription to Modern Drummer back in the 90's, they threw in a book that was a compilation of articles that Rick Van Horn wrote for the publication. It included plans for a "portable" riser. The plans called for a 1/2" plywood top and a base made with 1x2's. Well, 1/2" inch didn't cut it. Rather than scrap what I already made, I decided to add another 1/2" to the top.
It weighed a freakin' ton (technical term) so I pretty much kept it in my drum room for about ten years. Last year I saw a thread about using 5-gallon buckets so I decided to modify what I already had. I demo'd the base and used the wood for the support pieces on the bottom side. I trimmed the top to fit my kit and cut it into thirds. I also re-used the piano hinge from the original design.
I used the original riser on a gig once and it took two people and a couple of furniture dollies to move the top. Now each piece is manageable and moving the pieces is easy now that I have the Rock N Roller cart.
The screws aren't self-tapping, just regular wood screws. 3/4" I think.
Edit: The screws holding the lid aren't regular wood screws. I forget what they're called but the heads are rounded and are flat on the bottom but the shaft is like a wood screw. I drilled a pilot hole for each screw. I used fender washers to hold the lids in place. Also I forgot to mention that there is a piece of plywood underneath each lid so that the lids didn't get deformed when I screwed them to the top. Surprisingly, the buckets attach and detach pretty easily.