while clearly, effective instructions per cycle depend on the workload. That said, https://en.wikipedia.org/wiki/Instructions_per_second mentions AMD Ryzen 7 1800X reaching "304,510 MIPS at 3.6 GHz", which would give you a budget of 152 instructions in order to achieve 2 billions of operations per second (I assumed you took the plural to mean "integer plural", i.e. at least 2 billions :-) )

Now, I agree that it's a bit of a stretch to assume DOM operations won't hit some memory fetch bottleneck or something else, but parent's estimate is not miles off.