I always wanted a long picnic table, and this design was just perfect. It was my first real project, and it wasn't very difficult.
My first step was to sand all the wood to 180 grit, then finished it with Sikkens Cetol 1, natural color. Made good use of a 12" miter saw, could not have done this without it. Dealing with 4x4s is a bit harder than 2x4s. Used lag bolts where called for, on both the table and the benches.
About $1,000. Cedar in my area is very expensive. The 2x10x10' boards were $90 each, and the 4x4s almost $36 each. Add the benches, and $80 for stain, and the cost gets up there.
Started in June, finished in October. But I did have to take part of it apart to cut the legs down. I also only worked on it a few hours each week, mostly on the weekends. Since I finished most of the wood before assembly, and they required 4 coats with significant dry time, this took some time.
When I first completed the table, I realized that it was too tall (almost 34 inches). After much debate, I lowered the table legs so that the overall height of the table was 30.5 inches. For the benches I just basically followed the plan of the table, but used 2-2x6s and 1-2x4 for the seat.
Both the table and the benches are cedar with the table top being four 2x10x10' S4S cedar boards. Cedar 4x4s were used for the legs and braces on both table and benches. The seat of the benches are two cedar 2x6s and one cedar 2x4. The remainder of the structure for both table and benches was cear 2x4s.
I used Sikkens Cetol 1, natural color, for the finish. It really bought out the color of the cedar. Everything has at least four coats, but the table top has six coats. I finished all the pieces before assembly. The Sikkens requires 24 hours between coats, so with 4 coats, this took quite a bit of time.