The scams tend to push it to outright unbelievable levels, being scams and all that; but such offers are really only an exaggerated flavor of transactions we make routinely in the form of ‘loans’, ‘bonds’, etc.
In the context of an economy sufficent to support ‘time value of money’ a dollar today is worth slightly more than a dollar tomorrow and more still than a dollar a year from now or ten years from now. So the genre of “give me the cash I need now; I’ll pay you a greater quantity of cash at a later time” is wholly believable; it’s just…dubious…that time time-value of bitcoins is such that they appreciate by two factors of ten in 10 hours.
