Here's a hint If you don't want anything they're trading, or don't know what it is, I wouldn't suggest taking it.
Hold out till you get something you actually want!
Hoban's Hat is a limited edition. Rule of thumb is that ANYTHING that is retired will be worth more over time. Maybe a long long long time, but eventually. Best way to compare value by worth and not by rarity, is to compare battle stats.
Comparing using Battlepedia
bag of sand: 337.5K - 562.5K
Attack is +
fiery wand: None listed
Attack is Defense is
hobans hat: 975K - 1.625M
Attack is Defense is
Hoban's Hat is obviously the better battle item, and while TP has bags of sand at a million (over more) and Fiery Wand at 600K .. I'd keep Hoban's Hat! Makes sense money-wise, because TP has the hat at 2 million.
NO NO NO! Definately do NOT trade. You can get better NP for your Hobans Hat right now ... not to mention later on. It's BD icons are a great range in both attack and defense.