It's not the material that is expensive, it's the labor. Take the Topping rack for example. It costs like less than 40€. So how many hours of work would you be willing do for 40€?
(Another reason not to DIY is of course tools and equipment you need. It would take a lot of DIY projects for that stuff to pay for itself)
Last I knew, the Euro was steep to the US $, so let's say $60 estimate for your case in point. With black ABS pipe, painted PVC, or copper tubing to sheath all thread if you use it, or to use scrap wood as that is all the bigger these things are; it would maybe take no more than a couple hours, 3 boards, and some right angle brackets to make something functional.
Over here, the HD tech will cut your boards if you want, and then using the right angle bracket method, maybe 12 screws and you are done if you want a rustic look. Finish? Poly it, wait over night, and then screw it together.
I really do not see the issue. If tools or the store worker is an issue, I'm sure a neighbor would let you slice a couple boards or do it for you if you asked.