jimisand

Well buying at demo price should be close to resale of a used car really.  Anything over 5k below retail would be about right in my book.

TLDR: Be mindful of the demo start date. The warranty clock and mileage starts when the dealer puts it in service.
 
Do you use REDDIT? If so, check out the section called "R/AskCarSales" It's a pretty busy subreddit full of bored and honest salesman who help you a pretty good amount... They get this question probably a dozen times per day. I'd give it a shot... they really helped me alot, running free carfax, vin reports, and warranty reports just because i was chatty with them. just makes sure you say you're Canadian, they're sticklers about location. 
 
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Biggest thing to note is that the warranty has already begun. Say, if the FCA Bumper to bumper warranty is 30k miles, and there's 1.4k mi (2k km(?)) then know that's mileage you'll not get back...  also, the clock is ticking on the warranty as well. If it's been in their demo fleet for a year, then you can know that you've got one less year of warranty. You should be able to determine this from the Carfax, or by taking the dealers word for it.

When I worked at a Chevy dealer, we tried to keep the Demo/rental units below 2000-3000 miles.  To my understanding, sales will reduce the cost a proportional amount for the miles. In my opinion, Demos, even the rental ones, are not that badly beat on. If one's beat on, at least it was only for it's first thousand miles. Test drive it, and if it smells good (Not like weed), and you enjoy the drive (thinking nothing about the demo's history) I'd say keep it on your short list if the price is right.

Bear in mind that if it is a demo 2017 model it is not only used, but it is a full model year old.  Look up the black book value to get an idea what the resale value is.

Don't believe the 'dealer invoice'.  The invoice does not reflect the 'holdback'.  And beyond the quarterly rebates (which don't show up on the 'invoice') they also get a significant rebate (on the order of $4000-$5000 on Journeys) for their demos and loaner vehicles.

If you are buying the vehicle with a view to keeping it, note that the 7 year/115k Km zero deductible warranty costs the dealer less than $1700 - take part of your discount and apply it to that at their cost.  It gets expensive to troubleshoot and repair computer issues that surface as the vehicle ages.  To help mitigate electrical issues, which are usually due to corrosion, I strongly recommend you consider having te vehicle properly rustproofed - the treatments, when properly done will protect exposed electrical connections in addition to body panels.

knowing that figure you are looking for is a closely guarded secret and it varies as bramfrank has told you. that said you are buying a used vehicle , so it doesn't matter what you hope to find out what it is.What only matters what you are willing to pay and what they will accept. good luck on your quest...