diy arbor drapery

If that’s what you honestly want to do, I would bite the bullet and just pay the money. I think that much fabric could get pricey, plus then you have to fuss with it. If the venue or rental company that supplies the arbor has the fabric to do it, then go with them.
Then it is one less thing to deal with storing, selling, or giving away after the wedding.

A fabric store. Joann s comes to mind. A lot of people will say to order online but I find that it's hard to tell what the fabric really looks like. Unless you know exactly what you want and what it's called, then online is convenient and can be cheaper. Joanns.com is a great place for that, and often has 50% off coupons for up to 10 yards of fabric in one piece. You can order larger cuts but will only recieve the discount on the first 10 yards.

I’d rather just pay the $100.

But if you want to DIY I’d suggest going online, Joann’s fabric or Michael’s.

I’m not paying the $100 for 15 ft of fabric to be hung in an arbor... lol. We are already paying $1000 for drapery in the reception barn.

Emma- getting that much fabric at Jo Ann’s do they typically have a lot in stock?

Go to where fabric is sold and ask, the people there know what kind it is and they will tell you whether it'll cost more than $100. Fabric is $$$ and if you don't get the length right, you'll have wasted your money if it's too short.

The whole point of it is to find something less than $100. And we already have all of the dimensions so I would not be wasting my money

I ordered a bolt from efavormart for 20.00. It is 90’ long

If the arbor is 9 feet tall then you will need a lot more than 15 feet of fabric if you want it to drape like in your picture. That would be at least 18 feet for just the sides. Then you need a lot for the center to wrap around the beam and let it hang. Usually people use chiffon to get the loose flowy effect like in your picture. Joann's might be a good place to at least get an idea of the pricing but I would think based on the amount of fabric you'll need plus the time and labor to drape it yourself that the $100 sounds reasonable.

Joanne's is amazing for this type of thing. I'm planning to do tulle, to match my dress, on our arbor. It should cost about $10-15 for that much fabric which I assume is 9 yards, or 27ft, around the whole thing. If you want to use a solid material I'd say a good estimate is $35-50 (or more) for the whole thing. This sounds weird but I've also seen beautiful arbors where a low cost white bedsheet was used.