i've been told to expect about $300 a pier. i had all-pro foundation and du-west foundation come out. all-pro wanted to put in 5 piers, but said their minimum charge is $2500, so they'd add root barriers to get it up there. du-west said the problem isn't severe enough.
How old is your home? Most builders offer a 10 year structural warranty. My house had 7 piers installed through Advanced Foundation repair, and the builder covered it....was around $3,600. I like Advanced because they have a lifetime transferable warranty.
I just had some work done. I have a 75 year old pier and beam. I used On the Level Foundation repair. Their price was good and the sales rep was an Aggie. I had about 10 different companies provide estimates and also did my research on the BBB website before making a decision.
pier and beam work is real hard to get done because unless it's in real bad shape they can't make enough money off you to do it. I think I'm going to have to DIY mine in the next few weeks. That's one advantage of a P&B is that it's pretty hard to screw up.