There seems to be two ways to go about doing this:
1. Copy and Paste the table from Numbers into Pages, then in Pages, Choose File/Export, and save as an RTF or TXT file. The RTF seems to retain most of the formatting and most closely resembles tab-delimited text;
and
2. From Numbers Choose File/Export and save as CSV; all three options for saving yield the same comma separated value format. Next, locate the file in Finder, and click on the file name and change its tag from .csv to .txt; Click “change to .txt” to confirm, then open the ’.txt’ file in Pages (File/Open, or in Finder, control-click on the file and choose “Open With/Pages” from the pull-down). This method “tricks” Pages into thinking the file is a .txt, even though it’s a CSV.
Another intermediate step you can do with either method (to change commas into tabs) is to open the CSV with a text editor, and replace the commas with tabs prior to opening in Pages.
IMO, option 1 seems to be the easier of the two options.