Everywhere you look the advice seems to be that you should build your own pergola rather than buying a prefabricated kit or hiring a contractor to build it for you. There are so many resources to guide you through the process.
It is certainly a lot less expensive to do it yourself. You might even shoot for a higher grade material or adding on some options to increase the value of the finished product. All you need is a circular saw, a power drill, hammer, nails and then some fastener brackets. Of course, a ladder, leveler and another pair of hands to assist would be quite useful too. Even attaching it to your house is really quite simple.
Check out the information in the Build a Pergola section of the PergolaDIY site, take the survey, get a free plan, learn from the email series and then buy the book.
As long as you feel comfortable using the tools mentioned then it really will pay off to build your own pergola.