There was not much of a price difference going from a MK6 to the MK7. Hopefully there won't be too big an increase in price going to the MK8.
Keep in mind they have to compete with the other cars in the segment. For the golf... The Elantra GT, Focus, etc.
For the GTI... the Subaru WRX, Focus ST, etc.
The competitor pricing will drive the VW pricing. Remember that VW is not the luxury brand. That's Audi. VW has to compete as the everyday brand. Ford, Honda, Hyundai, etc. While we all know that VW has a better interior and so forth... They can't just all of a sudden say a GTI is now 8K higher than a Subaru WRX.
At the same time... the pull of the golf out of Mexico could be to free up production space for the Tiguan and Atlas. In the U.S., trucks and SUV/crossovers have taken over the market. There's articles about how the Honda Accord and the Toyota Camary have declined drastically in sales as the CRV, Rav4 have increased drastically. The market here for Crossovers is so high... that people don't even want a fit. They want the new HRV. Mazda released the CX-3. Toyota released the CHR.
Golf sales have been dropping along with a lot of other vehicles. This isn't a matter of "my GTI can do everything a Rav4 can". We on this forum are car enthusiasts. We care about performance and utility. That's why we know what a hot hatch is. Unfortunately, in the U.S. everyone else wants a crossover.
The real question is why someone made the decision not to bring the T-Roc to the U.S. Especially given how well Crossovers sell here.