Is the same quartz glass used to make the more expensive and the more affordable bangers?

Yes, quartz is quartz and anyone who says different needs more education.   Most quartz is made in China.  It is then sent to the USA and is worked by Americans.

Affordable bangers are cheaper in price usually because they are fully worked in China, or they are using thinner quartz glass.   The thicker the quartz the better it holds heat.