I don't want to put anyone in an uncomfortable position with this question, but knowledgeable answers would be appreciated

I just bought a new 2004 SabreLine 36 FBS, fully loaded and I set aside $20K total for electronics assuming I take the Furuno current rebates. I'm talking to a local, very reputable full function shop in CT who can job the whole thing in my marina over the winter. His discounted hardware total is about $16,800 plus tax and a not to exceed number of installation hours (I'm ok with taxes and hours, too). We're about $1500 off on the hardware number to make my budget. He's offering to start this week, so I know he has people sitting on the bench since it's pretty slow around here right now.
I'm ready to walk away over the $1500, since I really don't have the money available to exceed my budget number, which I gave him outright (I've never done that before!).
Somebody here probably knows the markups on Furuno Navnet Radar/GPS's (3 total, 2 GPS, 1 radar), Simrad AP w/RPU160 drive, ICOM M502 VHF etc. Just would like to know, am I being unreasonable in walking away from this offer? What's a reasonable discount off list to expect on a job like this?
I'm walking away in any event if he doesn't make it under $20K, just wondering if I'm being a jerk.
I can source the hardware at dealer cost (part of my purchase contract on the boat) and job out the sensor/radar installations and do this myself over the winter, but I guess that years of subscribing to Marine Electronics Journal has me convinced that a CMET qualified organization is the way I want to go, and as a business person I acknowledge that he deserves a reasonable profit so he can sustain his shop.
Opinions....?