If I fill 2000x2 cells on one sheet, and 1400x548 cells on a second with the formula: =ROW()*2000+COLUMN()*10 and save it in Excel 2007, the file size is 6,545 kb. If I copy all those formulas and Paste Special | Values and save the file, the file size is 3,897 kb.

So, a mix of formula and raw data would be somewhere in between ... I would guess. We have a fair few megabytes still to find.

What and where is this 600,000 data points?