Not my experience. I've used a bunch of stuff, and I can tell you a RasPi is what, 10W under load and 4 idling? A repurposed laptop (with a dedicated GPU but screen off) was 11W idling and 45W under load, and a repurposed desktop was about 40W idling and 120W under load.

You maaaay be able to find some laptop with an efficient CPU and iGPU that gets into the realm of a RasPi, and I guess the "identical storage" qualifier helps if you're adding a bunch of heavy storage to the Pi to bring total consumption up and lower the percentage gap, but my real world, real time measurements don't quite match that.

That said, if you already have one of those things and not the other the power consumption difference is fairly small in absolute numbers. You may save more money by buying a slighlty better lightbulb for your living room lamp. Definitely recycle whatever you have lying around that will still do the job.

My napkin math is similar, although I do wonder about transcoding machines where the old one is using CPU vs newer solutions in the GPU.

Used an old eee701 as a server for a fair while, pretty sure that was equal or less power usage than the Pis at the time.