A colleague of mine sent this to me and thought my input might be helpful.
I am going to disregard specific manufacturers, as with like any other industry, some make good products and others make bad products, so in this instance, I will only relay information regarding installation and costs.
Most installation contractors are going to have a minimum cost just to go out to the site. It depends on their overhead (wages, insurance, machine, truck/trailer, etc.) and travel distance. This minimum charge can vary from around $3,000 - $5,000. Since there were only six piers installed, this would fall under a minimum charge. If the general contractor marked up the bill, it was not much. The general contractor would generally be responsible for marking pier locations, oversee installation, and do their job as a general contractor, so I do not believe you were taken advantage of. The cost I see mentioned in the dialogue is $21 a foot. It does not specify if this material only or material and labor. A quick calculation shows $21 * 14' = $294 a pier. Being in the industry for over 20 years, that number is way, way too cheap. I understand it is for a deck so it is probably round shaft, 2-7/8", which would require two bolts for connections. Also, if the material is hot dipped galvanized, that adds roughly 7% to the material cost. Like someone mentioned before, the number of piers installed at the site is going to have an effect on the "per pier price". You can take it upon yourself to price pipe, hardware, steel plate (for helix) and estimate cutting and welding costs. You will find that a piecing out the steel and estimating transportation and manufacturing costs, it will probably come out to around $250-$300. This number does not include labor. I know the work does not look like much but there is significant investment in the equipment. You did not mention the number of helices so I will assume one helical plate.
This is how the bid will work on lets say 10 or more piles - $500 per pier. After 12'-15', depending on lengths of material, it will $20-$25 per foot after the initial depth. These are prices for typical residential projects requiring ultimate loads of 40 Kips or less. If there are no soil borings or a trial probe was not installed, no one is going to know how deep they are going to go until it gets in the ground. Installation torque will be monitored, or should be, through the entire installation process. The other item not accounted for in the cost, is the termination cap. It will require one of these and it can cost anywhere from $35 to $100 depending on the requirements. Those are also not typically galvanized unless it is terminated above grade and exposed to the elements.
As far as getting an engineer stamp on documents or plans, it is going to vary by municipalities in regards to their requirements. Some require it, some do not. You would be surprised at the number of cities who require nothing, and I'm talking large cities. Residential construction is not the same animal as commercial.
In a nutshell, I do not think you were taken advantage of. I do not know the character of the contractor and was not there to hear the discussions, however, on the surface and the content displayed on this message board, it does look like you were given a fair price.
My advice would be this:
1 - Ask for a pier log stating manufacturer of helical material, size of shaft, helical configuration and termination depth.
2- Ask for installation torque. Most contractors will just right down the last reading on their gauge. There is a direct relationship between torque and capacity of the piles.
If you are asked why you want this information, tell them that you may decide to do some additional work on the deck at a later date (add fireplace or whatever) and you want to know what the upper limit of the piers are to ensure they are not overloaded. Of course, you can tell them you want the information because you paid for it but my suggestion lets them know you have some foresight and not overtly stating that you distrust them.
