All these are taken from my pages. I put this here to start an arguement!
I will attempt to formulate some equations for getting the piece values. Most of them are based on logical reasoning (which you may disagree completely with), while some others are just my preferences

My system assumes that all the differences between the left and right of the inequalities are very small, and therefore are assumed to be the same, which is denoted by a.
P =Pawn, N = Knight, B = Bishop, R = Rook, Q = Queen, a = unknown constant
Inequality Equation Reason
N > 3P ; N = 3P + a Knights are slightly stronger than 3 pawns.
B > N ; B = N + a Generally, bishops are better than knights due to its range.
R < 2N-P ; R = 2N - P - a Generally, 2 minor pieces exert more pressure than a lone rook can.
Q > 3B ; Q = 3B + a The queen attacks laterally too.
Q > R + B+ P ; Q = R+ B+ P+ a This is controversial. But the queen is able to cover all of the diagonals, which the bishop cannot.
Let's solve the equations. P = 100, a= any reasonable value.
In this table, a is assumed to be 10. The biggest value overrides others to satisfy all inequalities.
Piece Expressions Piece Values , a = 10
Pawn P 100
Knight =3P + a =310
Bishop =3P + 2a =320 320 Overrides smaller value.
=3P = 300
Rook =5P + a = 510 510 Overrides smaller value.
=5P - a = 490
Queen =9P + 7a = 970 970 Overrides smaller value.
=9P + 4a = 940
The main idea in this is that a is relatively small, and are therefore quite equal.