I am king of all trades. I'll do any job for much less $ than a contractor.

With a new line of pipe running outside and all the necessary fittings your total materials cost is maybe $250. Since I am out of work, I would only charge you $10 an hour, or whatever you say is fair for unskilled labor in your area. I would make a hole in your exterior wall with a hammer because I do not have all the fancy tools they use on TV. I would spend about a day working on your house, maybe two. I fix the hammer hole with spackel, caulk, or aerosol foam, the choice is up to you. You pay me $425 and I go away, never to be seen again.

Too bad you wasted all that extra money on the ripoff contractor. He'll just blow it on some stupid tool he can use to extort more $ from consumers.

Why would anyone hire a plumber with license and insurance? Just doesn't make sense if you know me! And I am everywhere!

This is tough due to the considerable difference in licensed labor charges throughout the USA. You most definitly want a licensed and insured plumber because they will be working on the most expensive investment of your life and the job will consist of electrical, water, drilling, and possibly be dangerous to the installer.
I would have gotten three bids and had the three companies come out to see prior to hiring for the job.
Research the company thoroughly before having them do the job.

Did the plumber include the additional backflow preventer that is usually required by code?

Did the plumber use a second discharge pipe instead of Y'ing into the primary as required by the directions?

If the answers are "yes" and "yes", then you probably paid about right.