It looks like I finally understand those
The explanation is the same as last time. Look at these two clues:
6.*The piece with the ruby cost 200 dollars more than the ring with the topaz.
9.*The ring made of silver cost 200 dollars less than the ring made of 14k gold.
First let's put clue #9 the other way around:
"The ring made of 14k gold cost 200 dollars more than the ring made of silver."
Now you can directly compare those two clues. Looking at your grid, you know already that the ring made of 14K gold is the one with the sapphire, so it is NOT the one with the ruby.
So you know that the ruby cost 200 more than the topaz and another than the ruby (i.e. the sapphire) cost 200 more than the silver ring. If you pair topaz and silver, then the ruby and the sapphire would both cost exactly 200 more than the topaz/silver ring, meaning two items in the same category would have the same price which is impossible. Therefore topaz cannot be paired with silver.