Not much?
People are acting like M1 destroys x86, but as AnandTech showed in the recent benchmark, M1 is trading blows with Zen 3 in single thread performance while having much larger core and process advantage (5nm vs. 7nm) thus being actually more expensive to produce.
Single core performance does not differ much between mobile and desktop CPUs these days.
Are there any workloads that requires or perform better with x86?
The difference might be way smaller or non-existent once we see some comparisons with latest AMD offerings (especially when we have also CPUs with comparable process).
The M1 isn't a tiny power-sipping mobile part - it sucks power down just like AMD's 15W TDP CPUs do. The efficiency gains Apple are getting here are likely to be the result of several factors, only one of which are the CPU cores themselves.
You also can't compare manufacturing cost and retail cost. But given AMD cores are both smaller and manufactured on older process, it's probably safe to assume AMD ones are cheaper to manufacture.