Cursed item cost. Magic items with negative effects.

So I've read through most of the posts on cursed items and none have answered my question but mostly because there doesn't seam to be a system for it.

So I would like some opinions on the following:

I want to give a party of level 5s a little gift without it being too uber and also something that they aren't likely to think of.

Earrings of telepathy (level 5 wizzard spell, CL 9)

So my math on these are. 5 (spell level) x 9 (cl) x 1800 (command word) x 1/5 (use perday) x 1/7 (1 use per week). = 3085 ish, so call it 3100. That's for each earring, so as a party it would be 4 uses a week so plenty to be usefull and shouldn't be overpowered. (Comments apreciated on that)

I was hoping for something worth a bit less and I like there to be negatives to the stuff they are given so -1 con, or -1 will save would be 1000 gp (1000 x bonus squared). Does subtracting that from the cost sound fair (3100 - 1000 = 2100 gp)? Should I deduct a bit more for it being cursed (double cost for nonslot item so 1/2 cost for unremovable slot item?). The original idea was for them to all be part of a single item but worn by everyone, but I still wanted cost around 2k or so.

Well comments are greatly apreciated.

Thanks

I always liked the quirk that makes the user's hair grow an inch an hour.

Cooler curses that could be item specific:
5% chance of swapping bodies randomly between targets when activated, effects last 1d10x6 minutes.
only function when all communicating parties are stationary.
Only function when all communicating parties have drunk at least 1 alcoholic beverage.
Becomes non-functional if wearer has drunk alcohol within the last 24 hours.
when in use the person with the highest Int takes a -1 penalty to that attribute and the person with the lowest Int gets a +1 bonus. Ditto wisdom and charisma.
when activated, 10% chance of a random user getting a shield other effect placed between them and another random user.
All communication is automatically translated into goblin, and is full of obscure slang.

PS: Earrings translate into each user's native tongue, and are intelligent items which take liberties with the translations.