eesh I don't know. If I add up all the major components...
Display, $130
pressure sensors, $36 each (x2)
Temp sensors, $20 each (x2)
Case (display), $15
Arduino, $10
Case (Arduino), $15
Various hardware, $25
About $307 plus throw me a bone for my time your talking about $400... Is that really cost effective?
The display is a 4.3 inch display but they also have 5 and 7 inch displays so pick your poison.