If it were ARM1 or ARM2 it could have been 1 cent: those cores have long past their patent expiry dates, and if you recreate the cores using a free implementation (e.g. the open source Amber core, which implements ARM2) there is nothing you need to pay other than fab. If you can squeeze the economy of scale up you get that price point.
ARM7TDMI was 1994. That should be out of protection now.
Although if ou use RV32IMC it would have the same benefit.
Just RV32IM for ARM2 equivalence. C gets you to competitive with Thumb2 on code size, and better and much cleaner than the mix of ARM32 and Thumb1 you need on ARM7TDMI.
Cortex M0(+) is of course almost exactly Thumb1 without any ARM mode and just a couple of extra instructions to handle system tasks.
I expect ARM2 code is a bit more compact than RV32IM -- they do get some benefit from predication, the free shifter on the 2nd argument, all those addressing modes, and LDM/STM. But RISC-V gets a decent size and speed benefit from the single-instruction "compare two registers and branch" instruction. And ARM needs to spill variables to RAM a lot more (and only passes 4 arguments in registers). I don't know if anyone has made a close comparison as ARM32 is basically obsolete and Thumb2 is what everyone uses. On RISC-V if you have more than maybe 1 KB of program code then it's a net benefit to implement the 16 bit instructions, so basically everyone does RV32IMC if not RV32IMAC (the Atomic instructions are trivial to implement if you only have one processor)