Maybe it’s just something they say to customers but when I bought my last tv from Costco the salesperson told me they’re the same TVs on the inside they put less hdmi ports or minor other details is because everyone price matches now for identical models so that way you can’t go in to Best Buy and demand the price from the big box stores.if it's a model made for black friday then yes, it will be cheaper but seems to vary in how they drop the price. Sometimes it's something stupid like not as many HDMI or USB inputs.
the last tv I bought from Costco on black Friday was a unit they usually carry throughout the year and was just a little cheaper than normal. I actually ended up with a smaller vizio vs the samsung or whatever else I was looking at because the samsung wasn't going to support upcoming changes in 4k and something else (basically obsolete when you bought it) whereas the vizio wouldnt natively support it but would at least display the content with a firmware update.