In Cortex M33 land $15 will get you an entire NXP (or STM) dev board. An MCX-A156 will set you back about $5 which is about on par with an STM32H5. You can go cheaper than that in the MCX-A lineup if you need to. For what I'm working on the H5 is more than enough so I've not dug too deep into what NXP's FlexIO gives you in comparison. Plus STM's documentation is far more accessible than NXP's.

Now the old SAM3 chip in the Arudino Due is a different beast. Atmel restarted production and priced it at $9/ea. For 9k. Ouch. You can get knockoff Dues on Aliexpress for $10.

Edit: I'm only looking at single core MCUs here. The MCX-A and H5 lineups are single-core Cortex M33 MCUs. The SAM3 is a single core Cortex M3. The RP units are dual core M33. If the RP peripherals meet your needs I agree that's a great value (I'm seeing pricing of $1+ here).

Edit2: For dual core NXP is showing the i.MX RT700 at around $7.