Hint Doesn't Make Sense.

[evessal]

I got stuck on one of the puzzles, and used a hint that didn't seem to make much sense to me. Here is the clue:

8. Of the specimen from Portugal and the spider that sold for $75, one was won by Isaac and the other was the darkback

I have 5 possible sale prices of $45, $60, $75, $90, and $105 for 5 different spider specimens, 5 different locations where these spiders came from, and 5 different people who bought them. In a previous clue I had eliminated the possibility that the spider from Portugal was sold for $90, which leads to this hint:

Clue #8: If Portugal does not equal $90, and Isaac and darkback can only be paired with either Portugal or $75, then darkback cannot be equal to $90. Mark the highlighted cell as FALSE. (+120 sec. penalty)

How can that be the case? I've attached a photo and according to the puzzle there are no errors.

[Six8ten]

Work it backwards from clue 8. Shorthand:
darkback = Portugal or $75.
From other eliminated options, Portugal can only be $45 or $60. Substitute (45 or 60) for Portugal and you get
Darkback = (45 or 60) or 75.
The other options must be false. You can do the same for Isaac to eliminate some options on his column, too.

[evessal]

Work it backwards from clue 8. Shorthand:
darkback = Portugal or $75.
From other eliminated options, Portugal can only be $45 or $60. Substitute (45 or 60) for Portugal and you get
Darkback = (45 or 60) or 75.
The other options must be false. You can do the same for Isaac to eliminate some options on his column, too.

Thanks! Now I get it. So Darkback and Isaac can't be $105 either.

Thank you for the assist!