According to Wikipedia, the Commodore 64 sold 30 million units during its lifetime. Each of those units came with 64 kilobytes of RAM. Today’s home-use machines have 1-4 gigabytes of RAM.
64-kB = 65536 bytes
1-GB = 1073741824 bytes
That’s a ratio of 16,384 times. For 4-GB it goes up to 65536. In other words a machine with 4 gigabytes of RAM has the equivalent RAM of 65,536 Commodore 64s.
All the C64s in the world had a total amount of RAM equal to 30,000,000 times 65536, which is: 1966080000000 bytes, or about 1.8 terabytes. Some consumer hard drives are at the 1-TB mark now - the same amount of storage as the RAM in about 15 million C64s. I can see the day coming when my personal laptop will have more memory than the total from all the C64s ever made.