I am not saying your conclusion is wrong, but:
- CPU caches are wired much more complex than SRAM memory modules would need to be. It may be shared between CPUs, and being n-way surely requires silicon, too.
- if the ratio is way more than 10, why, then, do I find zillions of references stating that a) DRAM needs a transistor per bit, and b) SRAM can be built with 6 transistors per bit?
On modern CPU's, HALF- or MORE of the silicon is used to afford 4-16MB L3 caches. A CPU die is not much smaller than a DRAM chip, and a 1GB chip of DRAM is less than $10 these days judging by the prices of 16GB, 16-chip sticks of DRAM.