This type of scams always want us to send them some money in exchange. Some how through communicating with us, they can figure out how much they can ask from us and how they can ask us to send them the money. So, sometimes, they ask for very little money like 700 or 1,000 in exchange of sending us a large sum of money.
Don't communicate with them. These are scams and hoax. They come in many types and shapes. Sometimes, they even target some sub populations like disabled, etc. When we hear that some data is broken into. Usually, they are sold to these type of scam people. That is why they always have up to date information when they contact us.
Below are links of discussions for your reference.
1) The first link is a sample how the scam email works and how the communications can go on when we talk with them.
2) Here are some prior Just Answer.com question and answer sessions describing the details
3) Here are some discussions on how the scams work.