Complex sentence: This trend picked up steam as commercial Crayfords, while being relatively non expansive, proved to be superior for most rack-and-pinion devices bar the most lucrative, and became the default focusing device on many amateur telescopes just above entry level, and better.
Split into simpler sentences: This trend picked up steam as commercial Crayfords, while being relatively inexpensive, proved to be superior to most rack-and-pinion devices. They became the default focusing device on many amateur telescopes just above entry level, and better.