Well, if I look at the documentation (https://support.airtable.com/docs/identifying-blank-values) I would have to write Price = Blank(), to check if it is blank. And I am interpreting, that != Blank() would be the way to check if it is NOT blank. But like I said: I've been using != Blank() and NOT(Blank()) with different results. Confusing.
Well, to clarify what you're doing, what result are you trying to achieve? What field types are you checking for blank values (Link Fields, Numeric Fields, Email fields etc), and what is the output you're needing in the formula field that's checking if the target fields are blank? In my Not(Price) example, whenever there's a value a 0 will return, if price is blank then a 1 will appear.
Alternatively, in my formula field if I write;
Then this will return a 1 when my price field has a value, and a zero if price is blank.