A lot of China sellers stock goods destined for Europe in Czech as it is "central" Europe and has rail links to China.
Rail is slightly more costly than sea cargo but has is benefits such as being slightly faster and easier to get goods into that part of Europe (which can be cheaper than sea due to being landlocked)..
The Czech republic is in the Central Europe, as well as Poland, Slovakia, Hungary, etc.
There is not such thing like railroad from China to Central Europe yet. The rails from China to Europe end up on the Slovakian-Ukrainian border (a different rail pitch), for example.
The custom tax is not the most important part of the custom fee, afaik, as it is couple of % or none with electronics parts, but the VAT which is around 20% in EU. Afaik you now pay at ali incl. VAT and therefore you do not need the custom clearance basically.
PS: there is a plan to prolong the rails with Ukrainian pitch via Slovakia to Vienna, Austria, with a large cargo port near Vienna, but it is on hold.