i've completed every lesson.
Nice.
i basically use the 1,3,3,5,9 numbers:
only +8 for a promoted pawn, since you trade that pawn in for your new queen... i do think there's extra value associated with the bishop pair in an open position, since they are long range, have the ability to pin & are strong on both colors... +0.25 for each bishop seems fair, though i don't calculate it that way.
And their values in the past.
18th century (Modenese School): The earliest standard values were established, with the queen valued at 9 points, rook at 5, bishop and knight at 3, and pawn at 1.
19th century (Howard Staunton & others): Some early sources suggested slightly different values, such as the queen being worth 9.94, rook 5.48, bishop 3.50, knight 3.05, and pawn 1.00.
Early 20th century (Hermann Vogler): Some theorists experimented with alternative values, such as the queen being worth 10 points, rook 5.84, bishop 3.53, knight 2.89, and pawn 0.5.
you can read my post #76 at this topic
There is a reason why it is important to learn about the chess pieces' values. They help us a lot, especially in exchanges.
Why is a queen worth more than a rook and bishop combined?
That is a very good question indeed.
Seems that all the pieces' values depend on the position.