How do you determine how much DP a monster has for the purposes of building them?

Is it just arbitrary or is there a formula for figuring out a monster that will be a good match against a given party of X level?

Or is it just as simple as 600 for level One, 700 for Two etc...?

DP amount wise, it should be the same as making characters.

The DP for a monster you are creqatinig is based on thier level, just like a character. So if you want a monster to be 6th level, you would have 1100 DP to work with (1st level = 600 DP, +100 DP per level; or look at the progression bt level table on pg 23 )