I realize that signing bonuses by round varies and there are a number of factors.

Some of the factors that I'm aware of are:
HS player vs College underclassman vs College Sr with no eligibility left (which obviously hurts your ability to negotiate).

Also your position and team needs may affect.

But how does for example the range in the 9th round last year range from 25K to 250K?

I'm looking primarily at undergrad with eligibility left and the +'s and -'s.