That number could be all over the map depending on your goals and the cost of the throttle body. I TBI'd my T-bird for around $800.
Bare minimum for me:
$279 - MSII assemble it yourself.
$79 - 10ft harness.
$189 - LC2 Wideband O2
------
$547
Add $65 for a nice to have MapDaddy sensor for high boost (over 14psi) and "better" barometric correction. Then you may need a soldering station of some kind, $60 Simulator for testing during assembly, power supply for the desk (I just found an old router or such cord that provided 9-12v and cut it up).
Alternatively, an assembled microsquirt and harness is $339 for the short harness and $369 for the long harness.
The throttle body could be a pricey new unit, or a cheap one from a junkyard 4.3L/Chevy 305, or ebay score.
Likewise for fuel pump, you can junkyard it (I ran a $30 junkyard pump for over two years! And only replaced it because I was going racing so it's now a spare), or a new one is around $80 depending what the TBI requires for pressure.
Then likewise for sensors. Assuming the TBI has a TPS sensor built in, you just need a coolant and intake air temp sensor, which I tend to grab from the junkyard because they rarely fail and will come with the pigtail. The Microsquirt will require an external MAP sensor, which also can be sourced via the junkyard. These can be sourced from about any GM car/truck from the late 80's to yesterday.
So the cost can be as low as $528 (Micro+LC2) plus parts scrounging which can be as low as another $100 or as high as you are willing to spend.
