Data export is not that easy. I've looked into it for my own project. You have to determine which database fields you need to include in the export, what format those fields should be in, and then format of the export.

After you do all that, you need to code and test the export process. I estimated several days if not a week or two to get a workable system in place.

Edit: This is for a Rails project. If it was PHP, I wouldn't even bother thinking about it.

Not to mention the need to set up the actual page layout, markup, and related code... this is a PHP app so it's not that easy. Since I'm the only developer/everything else guy, my time has to be split between customer support, development of cashflow-generating features, and everything else needed to run a business. Maybe you're the "check out the Turing-test-passing AI I developed in a weekend" kind of programmer, but I'm not that good :)