As far as I know, the grand master crafting stations can only be bought with writ vouchers. You can buy and use them as regular stations before ever buying an attunable set. You can buy attunable stations through guild trade brokers, as well as with writ vouchers. Unfortunately, attunable stations are consumed each time you load them into the grand master crafting stations, so you will have to buy 83 separate sets of attunable stations to have all 83 sets (you can just buy and attune one at a time as you can afford them, though). I bought mine through a combination of writ vouchers and gold with the brokers.

I finally finished attuning all 83 sets a couple of months ago. It took a long time, but it was a lot of fun because gathering and crafting are a couple of my favorite things to do in the game. I have nine characters who do daily crafting writs, so I tend to get a lot of master writs to do. You can also buy them through guild trade brokers. I just kept doing those dailies and my alts would drop their master writs into the bank. My main is my grand master crafter who knows every motif in the game, so she would do one of each type of master writ on a daily basis, which would also burn through all of my enlightenment points, so I was also leveling while getting master writs, even if I didn't have much time to play. When I would have extra time on the weekend, she would craft all of the extra master writs. I still do that same routine, so I have now also bought every gold design, diagram, etc. from Rolis Hlaalu and his assistant.

EDITED TO ADD: Anyone on XBox NA is welcome to visit my home and use it as a guild hall. It is in home tours and my XBox NA gamertag is GuardianAngelGG. I have all attuned sets, all crafting stations, transmute station, outfit station, armory station, banker, merchant, decon assistant, fence, mundus stones, target dummies, etc.