The relevant Wikipedia page has a large gap between 1961 and 1984, not allowing to estimate, even approximately, in what year the symbolic threshold of $1/FLOPS (or, as the wiki table puts it, $1bn/GFLOPS) was crossed. In this case the Soviet data points would be mostly useless because the price...

Some cartridges on older consoles (like on the SNES) had battery save in them, so you can turn off the console, come back some time later and continue where you left off. These use an actual battery that powers the RAM so it basically never turns off. But does that mean it can deplete over time?...