In my case, my spinning disks expanded approximately 4x each time I upgraded:

1.2 GB Hard Drive in a Performa from Sears

4 GB HD in a self-build AMD K2 tower

20 GB HD in a Dell laptop

80 GB HD in a PowerBook G4 that I upgraded to an SSD

For SSDs, the journey was not linear and my drive capacity did not expand every time:

256 GB SSD in the first retina MBP

512 GB SSD in 11" MBA

256 GB SSD in a 12" MacBook

1 TB SSD in a MacBook Pro

Even with the last 1 TB SSD upgrade, it doesn't add up to all the drives before (~1.13 TB)