It's called "santur" here.
The one I described is different in 2 fundamental aspect from harp and santur:
1. harp and santur (and piano as well) have static single-note strings, there's no frets to change the note and produce different sounds out of just one string.
2. with santur (and piano) you don't touch the strings yourself, you press them with a hammer (santur) and key (piano), which makes it easier, but takes away the possiblity of bending the strings, hammer-on/downs, and other cool techniques which are only possible by fingers, not keys or hammers.
I want to build an electric prototype.
A rectangular wooden flat board,
where the strings are installed on it, with wider spaces between them than conventional guitars.
I can make the board and pickups, frets, and bridge, but I must buy the strings.
Are they expensive?