If you need GPIO pins, ESP32 is good enough for lots of use cases. If you just need a small low-power PC, used enterprise thin clients and mini-pc's (google project tinyminimicro) offer more while still idling around 10W or less. Those can be still bought for like 40-100 USD with SSD and 8GB or more RAM included.
I think Raspberry Pi is worth it only for some niche use-cases with current prices.
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Yeah, you can also combine and use both and still come out ahead.
ESP32 handles IO and streams data somewhere else that does any processing needed on more powerful hardware.