The necessary data rate for these photo finish cameras isn't actually that high, because every "frame" is only 1 pixel wide. If the photo is 10000 pixels high,

The necessary data rate for these photo finish cameras isn't actually that high, because every "frame" is only 1 pixel wide. If the photo is 10000 pixels high, you need a datarate of about 10 Gbit/s at 40000 fps and 24 bits/pixel. RAM is plenty fast enough for that. Regular high-speed cameras that shoot a video are a whole other story, though.