The ePub file does not contain any information about the InDesign pagination -- that information is all left behind when the ePub file is generated. So your only possible way to do that is inside InDesign.
Inside InDesign it will be either point-click-clic-click ...a few thousand times or you script it with an additional tool like AutoHotkey or AutoIt that can open, select the first 10 pages and then save the selection to ePub and re-do-it in the next file...
If your files have a lot of consistency -- almost the same structure -- and you can live with separating the first chapter, for example, then you can open them up (unzip), and edit with "sed" or "awk" to have a smaller set containing only a certain specific part.