I've found the cheapest 75-inch TVs in the Cyber Monday sales, big-screen entertainment for as little as $379

Hisense QD6 75-inch | $699.99 $379.99 at Best Buy
Save $320 - This big TV uses QLED tech, has a 4K resolution, has a range of gaming and Dolby modes and costs less than $400. Other retailers offered a similar discount but have sold out, so stock from Best Buy might run out at any time.

UK:

LG UA7000 75-inch | $689.99 $449.99 at Best Buy
Save $240 - Back to Best Buy with this well-reviewed 4K display. Few retailers even have this model available any more, so if you want a set running the popular webOS operating system, this is a deal to jump on.

Samsung U7900 75-inch | $649.99 $449.99 at Best Buy
Save $200 - This is a nice big backlit 4K TV, and I've definitely recommended its smaller models in other deals posts I've written. This discounted price is way cheaper than I've seen other retailers offer Samsung's Crystal UHD behemoth for.

UK: £699 £649 at Currys

Panasonic W70 75-inch | $699.99 $497.99 at Amazon
Save $202 - Various models of this Panasonic set are for sale, with this size option $2 lower than the price it was selling for over Black Friday. That's for a 4K set that runs Fire TV and supports HDR10+: a modest feature list.

Sony X77L 75-inch | $698 $498 at Walmart
Save $200 - Skating in just under $500 is this feature-heavy Sony set which features lots of the brand's killer components. It's the first set on this list with a 120Hz refresh rate and it seems that the 75-inch model is quite hard to come by right now.

Hisense QD7 75-inch | $799.99 $597.99 at Amazon
Save $202 - This is better-specced version of the TV lower on this list, enjoying time at the lowest price it's ever sold for. If you need a 144Hz panel or want to see Mini-LED, this is the cheapest option available to you.

Samsung QLED Q6F 75-inch | $899.99 $599.99 at Best Buy
Save $300 - Not many retailers have this size of the Samsung Q6F still available. It's only 60Hz but the panel is QLED with resolution and color upscaling, so it'll be great for watching TV shows and movies.

UK: £1,099 £778 at AO

TCL QM5K 75-inch | $1,199.99 $599.99 at Best Buy
Save $600 - This is certainly the biggest dollar saving on this list, with TCL's 4K QLED and Mini-LED getting a 50% price cut. Most brands are focusing on discounts to other members of TCL's TV family but this is certainly the best price cut.

Sony Bravia 2 II | $899.99 $798 at Amazon
Save $101.99 - This TV from Sony's impressive Bravia range has some unique PS5 features and access to more Sony apps, perhaps offsetting the fact that this modest reduction doesn't bring the Bravia 2 II down to its lowest price from the past.