We still must understand, why does the bridesman have to buy the paper himself? The answer is that the king loves his betrothed so much that he never believed the lashon hara about her. As far as he is concerned the marriage contract still exists. Therefore he doesn't want to buy new paper in order to show that as far as he is concerned the marriage was never annulled.
As far as Hashem is concerned the first luchos are still extant, they were only broken from Moshe's side, therefore he told Moshe פסל לך - Hew for yourself, because as far as I am concerned the luchos were never broken as my love for the Jewish People is immutable.
That is the meaning of the words that conclude the Torah לעיני כל ישראל the luchos were only shattered from the viewpoint of the Jews whereas as far as Hashem is concerned they were never broken.
Every morning when we wrap the tefillin strap around our finger we say וארשתיך לי לעולם - You are betrothed to Me forever. The tefillin are like a wedding ring with which Hashem marries us. This love is eternal and no external circumstances can change this.
[Rav Charlap Mei Marom 13/25 and the Klausenberger Rebbe]