For just 50$, BQEYZ no doubt worth every penny. Relatively balanced sound in an eye catching and durable shell. Textured and dell defined Bass followed by crisp vocals. Non fatigue and ideal for daily use. String instruments really sound great on it. KB100 performs really well in every scenario, either music listening or watching movies. And yes in 50$ price range KB100 is really a chi-fi gem.

My full review - https://www.head-fi.org/showcase/bqeyz-kb100.23369/reviews

Sounding of KB100 vigorous, juicy and harmonious from pleasant, easy V-shaped frequency response. Earphones win back all musical material on a positive, with a good rhythmic basis and worthy transfer of an emotional part.
Compositions move in details, with a due pressure and a good portrayal of textures. It is quite beautiful and melodious giving of a sound.
My full review in Russian:
http://audio-ph.ru/reviews/vnutrikanalnye-naushniki-bqeyz-kb100-tri-soldo-v-muzykalnuyu-kopilku

"The KB100 is a smooth iem that is able to provide a punchy bass reproduction, elevated midrange and controlled treble. It ensures a fatigue-free and relaxing listen session with good musicality. In addition, it utilizes a detachable cable. The BQEYZ KB100 presents great value at its price point with an enjoyable sound."

https://audio123blog.wordpress.com/2018/10/16/bqeyz-kb100/