I'm an amateur so can't really justify a real logic analyzer, but my hacked up sketches and python scripts for the Arduino have nothing on this level of polish so definitely going to give it a try next time!
Here's what the project's README says:
So, how the heck the pico is able to achieve this? Well, the key are the PIO units, these units are a wonder, they are coprocessors explicitly dessigned to handle IO, it uses a very restricted and deterministic assembler (only nine instructions that each take a single cycle to execuet) but extremely efficient, so efficient that with only two instructions is possible to create a loop that captures GPIO data up to 30 bits and redirects the program flow based in the status of one of these GPIOs.
Notably the PIO feature on the RP2040 is used to avoid having to sample input pins using the ARM CPU (which would make it slow and undeterministic). The sampling is effectively hardware-assisted using the PIO feature. The github page in the link goes into some detail about it.
They work with the open source sigrok software and basically just DMA the io to the host, thus the sampling rate and the cost, but can record for dozens of minutes.