Xanathar's "guidance" for magic item prices is woefully under baked. The amount of gold given out (even in standard, official 5e adventures) makes purchasing even the most potent magic items possible with pocket change.
Does it?
You said that your party is level 6, yes? So, I checked a bunch of standard, official 5e adventures and if a party of seven hits 6th level with enough gold per character that "makes purchasing even the most potent magic items possible with pocket change," that is completely DM's choice, because none of the adventures that I am scanning have anything like that amount of treasure.
The "most potent magic items possible," i.e. legendary items, should cost an average of 175,000 gold each. But let's assume that you were exaggerating and take that down a few notches, to just rare items. They should cost, per Xanathar's, 11,000 gold each on average. And your players have that as "pocket change"? At level 6? And this is 5e's fault? Okay, well if you have chosen to inflate the economy that much, why not just inflate the cost of magic items to go with it?
I happen to have a level 6 campaign going at the moment, and no one in the party has over a thousand gold; most have much less.
Edit: Okay, so I checked Forge of Fury, which is a conversion from an older module in TftYP, and the biggest treasure I found was this dragon hoard:
Nightscale has accumulated considerable wealth from her plunder of Khundrukar. Her hoard contains 6,200 sp, 1,430 gp, two garnets worth 20 gp each, a black pearl worth 50 gp, a
wand of magic missiles, a
+2 greataxe bearing Durgeddin’s smith-mark, a
+1 shield, a
potion of healing, and a
potion of flying.
And you can sell the axe for 6k! Nothing else in the module comes close, though a roper is the second best piñata, with about 2k worth of loot. 7 players could probably finish that adventure with about 1.5 in their pockets if they find/sell everything they can. That seems like a lot to me, but I don't see how we get from there to the "pocket change" scenario above.