You need to ask yourself if it is worth your time to even try and beat the quote they gave you. In my case it wasn't. Sure I could beat their price from a material standpoint (by only a couple hundred bucks) but instead I stood back and drank a beer while watching those guys sweat their *** off (in June) and they were in and out in 2 hours.
To rent I would have had to pick the unit up, haul it to my house (along with all the cubes of insulation), have someone come over my house to feed the machine while I was in the attic, staple in all the rafter vents, work in hot temps, get covered in blown in insulation, haul the gear back to Home Depot etc, you get the idea.
--Joe