I did a night at the TWA Hotel in November. I found pricing, in a runway room, on par with what I'd pay for a similarly convenient hotel at LHR. I paid £208 (approx.) for a night and, the night before, had done a stay at the Sofitel at T5 for £197.
It's convenient, being the only on-property hotel, and well-connected via the AirTrain. I landed in on VS to T4 and it took about ten minutes to get to the front door of the hotel. As someone else mentioned, it's also an Avgeek dream - and it ticked my boxes for old architecture, too!
The rooftop bar and pool overlooks the runway, too - even if it's cold, it's heated up there, and is well worth spending a bit of time up top. The hotel overlooks T5, so you'll see a lot of EK and JetBlue outside. My room overlooked two EK A380s and the runway was full of JetBlue. Had a good hour peruse with a coffee in the morning.
Be sure, too, if you do stay, to visit Connie, their '59 Lockheed Constellation. It's a bar now - you can just walk on. There's also a museum of TWA uniforms, the original designs for the hotel are around, too. And their coffee shop is Intelligentsia from Chicago, so it's not just rubbish beans. In the parking lot, too, there are some period cars.