The first bitcoins were mined at higher rate than today with 3 cpus. there is no minimum amount of work to pull out to mine a bitcoin, it's only relative to the network economic worth.
and gold in the times of the egyptians, romans and even upto the american wild west, were done via pickaxes finding gold nuggets the size of potato's
but now its more gold dust requiring shifting tonnes of dirt per ounce
someone with a pickaxe today will not get the same reward as someone with a excavator and sluice machine today