''Naknada troškova za održavanje žiga u vrijednosti za razdoblje od deset godina i za objavu podataka o žiga koji se održava u vrijednosti uplaćena je...''
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this is clearly about registering the trademark to preserve / maintain the legal protection afforded to it by registering it.

It is not about "vrijednost" in the sense of the "worth" of the trademark i.e. for how much it could be sold, or how much using the trademark contributes to getting away with charging prices that no one sane would pay for exactly the same product if sold as "no-name / unbranded".

IOW ***here*** :

vrijednost (žiga) = važenje (registracije žiga) = validity of the registration

as the whole point of "registering" is to give to the trademark a legal protection from misuse by others, it's often formulated as "maintaining the protection" (implied "maintaining the legal protection").

samples on the Web aplenty - search for "maintaining the protection of the trademark"


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Note added at 3 days 6 hrs (2022-07-29 16:53:59 GMT)
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Of course, "maintaining the legal protection" of the trademark is strongly related to / part of maintaining the "commercial value" of the trademak, but these are two distinct concepts, different meanings for "vrijednost".

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Note added at 3 days 6 hrs (2022-07-29 17:36:26 GMT)
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'Naknada troškova za održavanje žiga u vrijednosti za razdoblje od deset godina i za objavu podataka o žiga koji se održava u vrijednosti uplaćena je...''
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The compensation for the costs of maintaining the validity of the trademark for a 10 year period and publishing ... has been paid ...