I assume that's not an everywhere deal? I looked up the 56 inch box and its 1100 here in Michigan
I am not an expert, or an insider at HD.
but, from my interactions, it appears that there are at least three (four) "systems" in use:
1) there is the publicly facing web site. it is accessed thought homedepot.com, and through express.google.com. the reason I list them separately is that while the prices appear to be largely the same, there are deals available on one but not the other. as an example, there is currently a 20% off, up to 20$ total value, coupon for HD items available through express. note that not everything available on the main site is available on express. express also seems to have a floor of 15$ for free shipping, while homedepot.com is 49$. these databases don't seem to show a lot of discounted items. if they are listed at all, they are at the regular price. they will often show out of stock once the item enters the "discount spiral" that leads to a penny (or to the MET (merchandising execution team) removing them). this system usually lies about stock levels, reserving some amount of units for local sale. if it says they have three, they likely have five on hand, assuming no one has stolen any, of course.
this is why it is maybe four rather than three systems.
2) there is a "register" system available in stores to fixed location terminals (registers, SCO (self check out), price scanners (in locations that have them) and computers in various departments (pro desk, appliances, etc)). this is the database where you find those prices you see in screen shots here. this system is usually on a per store "view". if you want to see what neighboring stores have, you need to reset the location that the terminal is looking at (only available on the computers, not the registers or scanners). this view includes accurate stock levels, but again is only available on the computers.
this system is the most authoritative at the store level. what it shows as the current price is what the registers charge you. it is also the system that decrements the stock levels.
3) there is a hybrid system available in the hand-held units that employees have (assuming these are available everywhere, don't really know). from observing their use, these systems seem to take stock levels for the local store from the register system, but pricing from the publicly facing system. they offer easy access to checking other area stores for stock, but cannot see the prices there, they assume that the prices are the same between stores.
it appears that the MET can update these systems. on one or two occasions I have seen the prices on the hand-held units with a yellow background, and the "spiral" price listed.
the best place to check for local deals appears to the the computers. the best place to check individual prices (which I have occasionally found to be wildly off the sticker on the shelves) is either the price checkers through out the stores (in locations that provide them) or SCO (although I imagine that it will attract attention if you are constantly scanning items and then canceling and going back into the store with the item).
I am sure that this is incorrect in thousands of distinct and subtle ways, and I am also sure that various people who understand far better than I will chime in with corrections, but this will at least get you started.