I actually cannot take credit for building them. I am just not a handy person, I could likely have built a trellis that would work, but not these. I thought about it all winter, and came up with estimates of how much I would need to pay for the materials, renting equipment, etc, and it came to several hundred dollars, and that was probably a low estimate.
So, when it came down to it, my wife decided she wanted some new stuff in the backyard anyways, stuff I definitely couldn't do myself, and when we talked to the guy who is doing this stuff for her, I mentioned wanting some trellises, and he told me he could do them for me fairly cheaply. He actually has about an acre of grapes in his yard, so he knew what he was doing.
Based on my winter estimates of equipment rental and materials ( I was not going to use 6" posts either), I figured I payed about $100-$150 more than if I did it myself, and believe me, it was worth it if for nothing else my back!
This guy built it all in one work day, it would have taken me two or three weekends most likely. They put the posts in one day, then strung the wire a couple of days later.