This comment misses the point and doesn't compare apples with apples. This is a 2 seat aircraft designed to operate in the Light Sport category which is very different from an Ultralight. Light Sport aircraft cost $70k and up.
It was my first time flying such a primitive old plane and honestly I hadn't had such fun since my first solo. I was walking round with such a grin.
Old planes aren't bad at all. They are tried and tested, meanwhile this design doesn't exactly look as modern as a Diamond or similar cheap to run glider-come-airplane so it's hard to be excited in all honesty.
I'm assuming they're planning on making it a partial kit, and if you're expected to 3d print some of the parts $15k for "other" supplies (mostly avionics and engine) sounds pretty reasonable to me.