Believe me, if this was to be your wife's first attempt at machine quilting, especially a queen size, the number of quarters she would have put into the cuss jar would have been plenty to pay someone else to quilt her top, not to mention the stress she would have taken out on you, and that all the do-overs might have ruined parts of the top she did such a nice job on. She might never make another one.
When we pay someone else to quilt a top, we must remember that, like any independent business person we are not paying only for the hours for that service, but for their overhead -- they had to buy the machine, supply the space to set it up, pay for lights, heat, taxes, insurance (health and homeowners), maybe Social Security, etc. At this point, $170 looks like a bargain to me.