One thing we've noticed is the other side: it's often cheaper to just buy the movie, watch it at home (home-popped popcorn) and throw away the disc afterwards than it is to watch it in the theatre.
Home movies have gotten so much cheaper than theatres that this is feasible for most movies. We still see the odd one in the theatre, but that has gotten quite rare over the years.
You actually have something there. HDTV's are relatively cheap compared to the original vacuum tube variety that was used for standard definition. Even if you want to buy a 4K HDTV over the now standard 2K (1080p) 15:9 aspect ratio HDTV's you may pay about 10% more. In fact it is possible to set-up a reasonable home theatre (includes HDTV, DVD/BD player, amplifier and speakers) system for under $2000. Of course you could spend ridicules amounts of money on a home theatre system as well.
If you are into watching movies it is actually cheaper to either rent or if you think you may want to watch the movie again then purchase the Blu-ray. Even if that movie is the latest release and costs say $30 it would still be cheaper to purchase and watch with friends and family than go to a movie theatre.
It probably would be cheaper over the long-haul, plus you don't have people standing up in front of you in the middle of the "closure" scene just to beat the queue to get out... argh, so inconsiderate! Also, you can pause it at any point to talk, make tea or go for a piss. And you don't have to spend time and money travelling to/from the theatre and parking. I'm poor so I neither go to the cinema nor have a big home cinema system, but that'll definitely be my preferred choice upon leaving poverty