Crafting plays a vital part in Final Fantasy XIV's economy, as players who have leveled their Disciple of the Hand jobs are responsible for filling market boards with the endgame gear, tinctures, and food that are used by those participating in higher-difficulty content. Some of the materials needed for these crafts aren't simply gathered out in the wilds, however, and cold, hard currency is required to acquire them.
Purple Crafters' Scrips serve as the endgame crafting currency for Endwalker, and players can exchange them for rare crafting materials not found anywhere else in the world. By exchanging level 90 collectables to any Collectable Appraiser found within FFXIV, players can then use these purple scrips to purchase crafting materials, gear up to item level 620, and crafting-specific materia.
While any gear bought with Purple Crafters' Scrips is bound to you the moment it is purchased, you can sell any crafting materials and materia bought with scrips on the market board. A few of these items are generally more in demand than others, such as specific materials found in food recipes used by Savage raiders, along with the materia used to meld crafters' best-in-slot (BiS) gear.

Best items to buy with Purple Crafters' Scrips in FFXIV's Patch 6.5
Here is everything you can purchase with Purple Crafters' Scrips at the Scrip Exchange of your choosing, broken down by category:
Level 90 Materials
Item | Purple Crafters' Scrips Required |
Immutable Solution | 125 |
Dark Eggplant | 15 |
Broccoflower | 15 |
Dragonfruit | 15 |
Pure Cumin | 15 |
Caviar Sturgeon | 15 |
Prime Loaghtan Rump | 10 |
Sunset Carrot | 10 |
Piennolo Tomato | 10 |
Thundermelon | 10 |
King Urchin | 10 |
Butterbeef | 10 |
Giant Pumpkin | 10 |
White Peach | 10 |
Subtle Cinnamon Sticks | 10 |
Glass Scallop | 10 |
While you undoubtedly need to acquire each of these items if you intend to complete the entirety of your crafting logs, two items in particular stand out in the list and can be useful if you take part in high-end content. If not, you can still sell them and the crafts they make for a healthy sum of gil.
The first is the Immutable Solution, which is one ingredient found in each of the Grade 8 alkahests, like the Grade 8 Strength Alkahest or Grade 8 Mind Alkahest. These alkahests are requirements for the item level 640 Diadochos set's recipes, each one belonging to different job roles depending on its "stat-type." While items like the Diadochos Jacket of Fending don't sell for as much as when they first arrived in Patch 6.4, you can still make a profit off of other players who have yet to acquire the item level 650 Credendum gear from Allagan Tomestones of Comedy.
The next is the Dark Eggplant, one of the rarer ingredients used in the recipe for Baked Eggplant. As of Patch 6.5, Baked Eggplant is considered the best food for nine of the Disciple of War and Magic jobs to gain the extra edge during high-end content. Whether made for yourself or the market board, the Dark Eggplant is one of the better choices for spending your Purple Crafters' Scrips on.

Item Level 620 Gear
Item | Purple Crafters' Scrips Required |
Afflatus Saw | 500 |
Afflatus Claw Hammer | 500 |
Afflatus Cross-pein Hammer | 500 |
Afflatus File | 500 |
Afflatus Raising Hammer | 500 |
Afflatus Pliers | 500 |
Afflatus Mallet | 500 |
Afflatus Grinding Wheel | 500 |
Afflatus Round Knife | 500 |
Afflatus Awl | 500 |
Afflatus Needle | 500 |
Afflatus Spinning Wheel | 500 |
Afflatus Alembic | 500 |
Afflatus Mortar | 500 |
Afflatus Frypan | 500 |
Afflatus Culinary Knife | 500 |
Artful Afflatus Work Cap | 300 |
Artful Afflatus Work Shirt | 900 |
Artful Afflatus Halfgloves | 300 |
Artful Afflatus Hose | 300 |
Artful Afflatus Workboots | 300 |
Artful Afflatus Earrings | 300 |
Artful Afflatus Necklace | 300 |
Artful Afflatus Bracelet | 300 |
Artful Afflatus Ring | 200 |
Like their Disciple of War and Magic counterparts, gear plays an essential role in performing well as a Disciple of the Hand. Many endgame crafts require a high Craftsmanship or Control stat, which can be found on high item level gear. The item level 640 Afflatus gear is a suitable substitute before crafting or purchasing a set of your own best-in-slot Disciple of the Hand gear.
Two other sets of gear are available in exchange for Purple Crafters' Scrips, one for each individual job with an item level of 570, the other a universal Disciple of the Hand set at item level 590. While cheaper than the Afflatus gear, they're best suited as glamour items at this point in Endwalker's life cycle. You'll find yourself needing the increased stats sooner rather than later, so it's best to purchase the Afflatus gear first if you can't afford the current BiS items, leaving the lower sets for later if you'd like to use their glamours.

Materia
Item | Purple Crafters' Scrips Required |
Craftsman's Competence Materia X | 500 |
Craftsman's Cunning Materia X | 500 |
Craftsman's Command Materia X | 500 |
The current best-in-slot (BiS) gear for crafters requires a whopping 22 Craftsman's Command Materia X's across its set, along with seven Craftsman's Competence X's. Attaching materia to a piece of gear isn't always guaranteed to succeed if you're overmelding, meaning that it's likely you'll need to acquire even more than what the open materia slots require. Purchasing the bare minimum of the two different types of materia will require 14,500 Purple Crafters' Scrips, but you'll find yourself in need of much more if you're unlucky. You can see the melds required for BiS Disciple of the Hand gear listed here:
With your gear properly melded, plenty of other players still need large amounts of materia to also achieve the best-in-slot gear melds. You could always be generous and use your purple scrips for charity, but the demand for endgame materia could turn you a sizeable profit on the market board.