This is my version of a fairly cheap but stylish and expandable filament rack for one kilogram rolls. It cost me (Home Depot, Chattanooga, TN, US)

$41.46 plus tax. Other than a 3D printer, you'll need a hack saw or cutoff saw to cut the curtain rods in half. With the following items purchased, you can have two rows of filaments with room to add more:

Source: Home Depot (shelving department)

Brand: Everbilt

(1) sku number 820909902096, 48" closet rod to be cut in half (1 @ 7.98)

(2) sku number 820909902164, 48" rail (2 @ 7.98)

(4) sku number 820909911708, 9" arm (shelf bracket) (4 @ 4.48)

Cut the closet rod in half and attach printed caps to ends. Some smoothing of the rough cut may be necessary and the caps may need to be tapped on with a hammer.

Attach the rails 16" apart on studs at desired height. I used 2" stainless steel screws.

Insert the brackets at desired height.

I  used ordinary PLA.

Insert the 3D printed inserts into the brackets and push them all the way back.

(Opional) Put a dab of hot glue under the rods. Load the rack.