One of the reasons it’s so expensive to get an ultrasound is the piezoelectric components. They have to be carefully grown as a single crystal, which takes time and some advanced tech. Ceramic piezoelectrics are cheaper and easier to make by comparison, but not responsive enough.

Kicking this account off with a figure from my thesis! This is what I spent 4 years of my life on, figuring out how particles are aligned in nozzles to make more efficient piezoelectric devices: etda.libraries.psu.edu/files/final_...