Is my understanding of the websockets pricing model correct?

It’s my understanding that, if I pass a websocket to a durable object, I’ll be paying for 128MB of duration continually until the websocket is closed. Over the course of a month, this would seem to add up to $4.05 per average number of durable objects with connected websocket(s) per month; is this correct? It seems quite expensive just to keep connections open to me - continually polling 5 times a second might even be cheaper.

A WebSocket being connected to the Durable Object counts as the Object being active.

My understanding of the durable object being active 100% of the time it is connected comes from this sentence in the documentation, but this doesn’t agree with the pricing example below, which talks about the possibility of the DOs being active 50% of the time.