Soft 404
The Pico isn't that good at power saving. The Raspberry designers mentioned it wasn't one of their main goals.
The new SDK1.5 comes with some low power examples (in PicoSDKv1.5.0\pico-playground\sleep). I'll have a shot at measuring them.
quick check, each time with a 1.8V supply (power to VSYS). No debugger attached.
Dormant example
Sleep example
Hello World Serial (with nothing attached to the serial pins)
Hello Multicore
baldengineer did some measurements too, on a W:
Keep in mind my measurement was with a daily build of MicroPython. So, it's possible the consumption is a bit lower now.
But, as Jan Cumps said, the RP2040 isn't known for its low-power abilities. I think the datasheet value for deep sleep is around 1 milliamp!