Along with the ISK Doubling/Tripling posts this is one of the most common scams that appear in Local chat in the trade hubs. Like the Rage Quit one this scam relies on the greed and inattention on the part of the Contract Acceptor to work.
The contract issuer sets up a contract for an item or items, typically PLEX, for an amount that is missing three or more zeros from the actual value. So instead of offering 395m for a PLEX they'll actually only put 39.5m or 395,000.
Once the contract is setup they will then advertise in local that they urgently want to buy "[item(s)] for [x] ISK":
|Image credit to Broadscope Corporation Online|
A look at the contract shows 395 in the Get and a PLEX in the Pay, so it must be right so I'll just click Accept...
What Happens Now
The PLEX you had in your inventory is traded for the 395,000 ISK that the contract stated was what you would get instead of the actual market value for the item.
Not much else happens, you might laugh or curse but face it, if you Accepted the contract you traded that PLEX not for it's actual market value but for a fraction of that.
How Can You Protect Yourself
As with the Rage Quitting contract, spending a little time reading the details of the contract closely will help you prevent such a mistake happening. The green and red text are right, at a glance but reading the full You Will Get shows that you will be getting far less than you should be.
If you see a contract make sure you block both the issuer AND the person who advertises the contract (they could be different).