Well technically they are correct. A 1921 S graded by PCGS or NGC at MS70 could go for that and probably higher, even one graded at 68 may go that high. Problem is, those grades are almost unattainable.
Now your coin looks very clean, and even though I don't see the S mintmark on the reverse I will assume it is there. I won't try to grade it or tell you if I suspect it is genuine or not, that would have to be for a dealer who has it in hand.
Bottom line is yes, $1400 is possible. Remote, but possible.