After finishing the quests that take me through the hotel to get to the parking lot, I accumulated a fair number of champagne bottles, which I dutifully turned in for diamonds. Now I've got 8 diamonds.
The diamonds sell well to merchants (about $1500 iirc), but I've held off on selling any, since rare items like that usually have a better use than being sold for cash.
From this question I see that diamonds are needed for a mod later on, which does not surprise me. What mod is it, and how many diamonds will I need?
Can I sell some of my diamonds and still have enough for late game, or should I hoard every single one?