Sum the maximum values of cells in 4 columns (how to speed up the process ?)

Hello everyone, I just signed up and I always rarely used Excel (so I know very few things), but recently I've been trying to finish a series of worksheets that I think is too long to be done manually so I decided to ask for help . Here is the situation: I have four columns and what I want to do is to calculate the maximum values of all their cells and then sum them. http://s2.postimg.org/7vnl9y3jd/Excel_Example.png

But here it's still quite easy even for me, the problem instead is that I have a higher number of columns (almost 5000) from which I want to obtain again the maximum values of the cells and the sum of the maximum values, and all this done always considering four columns at a time.
http://s2.postimg.org/7vnl9y3jd/Excel_Example.png http://s9.postimg.org/z2x6swydr/Excel_Example1.png
Here there are only the first eight columns, but, since are many more, is there a way speed up the whole process instead of replacing them all the times?

Thank you in advance.

Try placing this formula in the cell you want the sum.

=SUMPRODUCT(SUBTOTAL(4,OFFSET(A2:D1001,ROW(A2:D1001)-MIN(ROW(A2:D1001)),0,1)))

Modify the range as needed. Also, you can eliminate your MAX column once you verify this works.