Standard shipping rates for alu extrusions from Aliexpress are insanely high. Green Lin from Components Explorers can get you custom shipping cost. Contact him through Aliexpress or Skype. Example transaction below. Shipping cost was $65, delivery time to Poland 12 days, no taxes, no customs.
There is also european supplier operating from Germany, Motedis. They have flat shipping rate to Poland of EUR 25. All together it's second cheapest option.
Some people are sourcing extrusions from Andrzejewski company or ARMA https://arma.info.pl Ask your seller before because there were extrusions 2020 with 5mm and 6 mm groove. Extrusions with 5 mm goove needs a very expensive nuts, and these accessibility is dependent to your localisation.