This is the kind of thing I do for a living .
The max I'd pay is around 100 for a longacre or similar , but checked against the tpm in my car the $6 cvs digital one is accurate enough to measure in increments of one pound so that's what resides in the boxster .....
How accurate do you think you need it compared to how accurate do you actually need it are often worlds apart
Don't over think it .... Spend the money on gas instead !!!