"I don't think it's normal that I have to pay for the shipping costs" - Please read the following to understand why:
We strive to keep our prices as competitive as possible while maintaining the quality of our products. Offering free returns would significantly impact our operating costs, which would ultimately reflect in higher products prices. Our goal is to provide the best value to our customers upfront, rather than incorporating potential return costs into every purchase.
In summary: free shipping/returns will automatically turn into a higher product cost, because in the end we also have to pay the shipping company. Which makes our products no longer affordable for everyone, what we want to avoid.
Thanks for understanding.