You can get the next section no probs,its what i did. Price is roughly the difference between the two poles inc. end cap and delivery. I never take the extra one off though,i find it light enough and still short enough plus i often dont extend the first thinnest whippiest section unless i need to.
Got some skylights i can`t reach and considered a longer pole but i would get them by working off a step ladder for extra height(next time),that means money stays in my pocket as a longer pole would be a long time paying for itself for the odd skylight which ought to be done from the inside anyway or left.