You spend less when you shop for art supplies online, especially by comparing prices and looking for sales. Large online art supply stores often charge less. They have more customers than small, local art supply stores. They also have a larger selection and an easily accessible sales section. Occasionally I've received "old" unused merchandise, such as drier tube paint.
I take stock before ordering to know what I need, not what it would be fun to have like a new ink. Even so, I've acquired an abundance.
Using Non-artist Supplies
Use coupons whenever you can, and watch for any with a huge-discount-on-one-item. That's when I buy the expensive French Ultramarine blue gouache. I even google the store's name and "coupon" when waiting in line at Joann's and Michael's. There's always some discount to use.
While I generally avoid email subscriptions, you'll find a store's latest and greatest deals in their newsletters.
There aren't many ways to recycle scribal art supplies, but I do reuse pergamenata. I tend to start the calligraphy over on a scroll at least once, so I have unused first tries. When I have time, usually watching TV, I use a sharp knife and scratch off the dried ink. I use the reverse for another project.
Using the second side of perg works for me. I've seen comments on Facebook that ink feathers on one side of perg. Test the second side out before you spend the time it takes to scratch off a whole first side.
Buying in bulk is a great way to save. For that to work for me the items must be small, keep for years and be a staple item. I've learned fun or fad cheaply priced bulk items may be space hogs I forget and never use. It's better to buy quality materials in smaller quantities.
Another way is to have your scribe's guild buy in bulk and then give or sell the items to members. A few years ago the Calontir Scribes' Guild ordered huge pergamenata sheets. We cut them down and gave them to scribes after they did original scrolls. A thanks to scribes for their work.
I've learned the hard way taking care of supplies I already have saves me money. My biggest problem is dip pen nibs. While I try to clean and dry them after use I forget to do that when I'm cleaning up at day's end. I wash off brushes but forget my nibs. They aren't expensive, but they're not meant to be disposable.
It's also important to keep paints and inks out of extreme conditions. I learned ink separates if you let it freeze overnight in a car. One Lilies War a paint tube burst when I opened it. I've also had paint mold because I didn't let it dry out before I put it in a sealed container.
Having an organized studio would save me money too. There are times I can't find something so I order it. Of course that must happen before the lost item reveals itself.
When buying a pricier item, consider how you work. Many scribes swear by an easel artist case, but I don't work vertically. I also prefer to work in my studio, not on site. So an expensive art supply case is not for me, even though I think they look cool.