My answer would be, Yes.
That is a good price to have someone experienced do the install, they would already know all the tips and tricks and would do an excellent job (um the same job people pay $15K for).
I received the same offer from Roush, but ran into a few challenges. First, I live in Georgia, and would need to drive or ship the vehicle to Roush, which of course changes the $720 install price dramatically (they'll need the vehicle for atleast 2 days. So a shipper up and back could be about ~$1,200 to $1,600, or if you choose to enjoy the area for a few days you have the expense of driving your truck, renting a car and a hotel etc... Now, if you live in the area, and don't have those "additional" expenses, don't even bother asking just do it!
Now comes the Warranty conversation.. Here's what I was told from Roush. If you buy the stage 1 525HP and get it installed by a certified mechanic (not DIY) it will have the warranty. However, on the stage 2 version 590hp (my choice).. They will not warranty a third party install at all and "here's the kicker" the will not warranty stage 2 unless Roush gets the vehicle directly from the Ford production line. Basically, they don't know how the motor has been treated after the production line, and aren't willing to warranty the unknown.
I actually entertained the scenario of paying them $720 to install and $1,200 roundtrip for shipping from my dealers lot once I bought the vehicle and was told it was a "no-go" from Roush.. However, if you can get it done, and can get the warranty, the peace of mind down the road was well worth the $1,200 round trip shipping expense to me.
I just couldn't get that dog to hunt!