The FS32R274VCK2VMM appears to be the cheapest in this series; Digi-Key have it for $30, NXP has it for "$13 @ 10K". This is for a 200MHz part.
https://www.nxp.com/part/FS32R274VCK2VMM
https://www.digikey.com/product-detail/en/nxp-usa-inc/FS32R2...
The two related devkits list for $529 and $4,123:
https://www.digikey.com/products/en/development-boards-kits-...
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Those processors make quite a few reference to an "e200", which I think is the CPU architecture. I discovered that Digi-Key lists quite a few variants of this under Core Processor; and checking the datasheets of some random results suggests that they are indeed Power architecture parts.
https://www.digikey.com/products/en/integrated-circuits-ics/...
The cheapest option appears to be the $2.67@1000, up-to-48MHz SPC560D40L1B3E0X with 256KB ECC RAM.
Selecting everything >100MHz finds the $7.10@1000 SPC560D40L1B3E0X, an up-to-120MHz part that adds 1MB flash (128KB ECC RAM).
Restricting to >=200MHz finds the $13.32@500 SPC5742PK1AMLQ9R has which has dual cores at 200MHz, 384KB ECC RAM and 2.5MB flash, and notes core lock-step.
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After discovering the purpose of the "view prices at" field, the landscape changes somewhat.
https://www.digikey.com/products/en/integrated-circuits-ics/...
The SPC574S64E3CEFAR (https://www.st.com/resource/en/datasheet/spc574s64e3.pdf)
is 140MHz, has 1.5MB code + 64KB data flash and 96KB+32KB data RAM, and is available for $14.61 per 1ea.
The SPC5744PFK1AMLQ9 (https://www.nxp.com/docs/en/data-sheet/MPC5744P.pdf) is $20.55@1, 200MHz, 2.5MB ECC flash, 384KB ECC RAM, and has two cores that support lockstep.
The MPC5125YVN400 (https://www.nxp.com/docs/en/product-brief/MPC5125PB.pdf) is $29.72@1, 400MHz, supports DDR2@200MHz (only has 32KB onboard (S)RAM), and supports external flash. (I wonder if you could boot Linux on this thing?)