Are you... asking yourself? What did you decide?
BPF instructions could also each have an abstract relative cost with or without real value.
BPF in WASM (unfortunately without the kernel performance advantages or possible side channels) or the fwiu now-defunct eWASM might be an easier place to test the value of costed opcodes.
The [e]BPF verifier does not yet rewrite according to opcode costs of candidate programs.
"A look inside the BPF verifier [lwn]" https://news.ycombinator.com/item?id=41135478