Just found an old bill from the Vobis Data Computer GmbH: I bought my first computer, a wonderful Sinclair ZX81, on 11 Oct 1983 (when I was 11 years old). It cost 148 DM, or about 75 EUR.
It had 1 KB of RAM, a membrane keyboard, and a graphical resolution of 44 x 64 pixels. I computed Mandelbrot sets on it (Apfelmännchen) - it would plot one pixel every few seconds. The CPU (a Zilog Z80 running at 3.25 MHz) had to render the screen, and there was a FAST mode that would disable screen rendering and run computations 4 times as fast. Storage was on a MC tape recorder.
The 16KB RAM extension cost 85 DM. The MacBook Pro I'm writing this on, 25 years later, has about 125000 times as much RAM (a compound growth rate of about 47% p.a. - remarkably close to Moore's law!).