10 bit, 32 channel, 80 Msample ADC is <$300 [1] at prototype quantities, and <$150 at production quantities. 12 bit, 64 channel, 80 Msample ADC could be done with 4 of these [2] for $620.

An AM5716 or 5726 would be $30-$40 (although buying one is a little trickier). Thats 7-8 processors in one, plus 1-2 DSPs. Plenty of power to handle all the processing required. Even a 128 channel device should only be ~$2000 in parts (minus the transducer). One with limited capabilities should be <$500 (again, minus transducer). Much less if you make a few more compromises in the ADCs.

We can make SDRs for incredibly low prices nowadays, the only real difference between that and ultrasound is the number of channels. The only reasons ultrasound machines cost more than 5 grand are economic inefficiencies. The engineering has been solid for a long while now.

[1]: http://www.digikey.com/product-detail/en/linear-technology/L...

[2]: http://www.digikey.com/product-detail/en/texas-instruments/A...