What is the price difference in making a weld machine?

It really depends on the base metal composition and thickness.
GTAW(TIG) provides the highest quality welding in manual or semiautomatic processes. But it's also the slowest.
SMAW (stick) has advantages in wind, low equipment cost, no cylinder and high weld deposition.
Your question is hard to answer because the process is so different. You'll pay more for GTAW, but the quality will be higher.