I've just been offered four figures for a 4 letter Instagram name.
Is this a scam, or are short instagram names valuable? If so, how?
It's likely a scam. If the name is worth four figures now, you should continue sitting on it and see if you can turn it into a five-figure offer.
The value of the name should be associated with the brand possibilities, or the established audience.
I would be suspicious if this is a goblidegook name and you only use it for lunch pictures.