Estimates vary (because benchmarks and use cases vary), but it's generally faster than 50%. That number was seen here,

https://www.usenix.org/system/files/atc19-jangda.pdf

(I assume that's what you refer to?) It's a good measurement, but it's from 2019, and it's just on 2 wasm engines. There are other estimates, like here:

https://kripken.github.io/blog/wasm/2020/07/27/wasmboxc.html

That tries to measure the fundamental overhead of wasm's sandboxing as opposed to a specific wasm VM, and it finds just 14%.