I like the idea, but $350 plus a Pi plus getting electrodes is beyond my "impulse by to try it out" price for sure.
That said, doing an EEG on yourself is a bit disappointing imo; You won't get much interesting output.
8 channel headband with individual gel packets for each electrode. You pop the gel packets and then you have wet electrodes!
The company is called Ceribell; Happy to answer more questions if you have them. We do not sell to individuals, but if you're in the research space, I'm happy to get in touch.