If it's not, you can drop the cost. There are AVR like 8051s that you can get for 10 cents.

I can't find any 8051 less than 30 cents and I digikey sells attinys for 17 cents.

I haven't confirmed what you've said yet, but it makes sense since 8051/8052 MCUs are generally used for their compatibility with legacy code.

I've been working on an agricultural spray controller that uses some silab part only because there is already assembly code written for it. The company that sells the controller doesn't want to spend the time rewriting it in C and moving to arm or pic.

That doesn't explain why you suggested a more expensive chip.

What's cheaper or not depends on your volume at that level.