Those brain electrode things... how much do they cost?

Factual Questions
1

Those electrode things they stick to your head that measure the EM activity of specific parts of the brain, and any other electronics necessary to get the readings… how much do they cost?

You know…when they stick things to your head and plot out a sleep cycle… Is that kind of technology prohibitively expensive per unit?

Thanks

2

I think that what you’re looking for is the BIS from Aspect. It measures the EEG and then performs some FFT and black art on the signals, to get an index from 0 (out cold) to 100 (fully awake).
I have no idea how much they cost, but I know that at the time the machines themselves were relatively inexpensive, but the sensors were where they earned the money.
The problems with measuring EEG (as opposed to ECG) is that the signal amplitudes are so much smaller. We’re talking a few mVs so the sensors have built-in pre-amps.