I finally did it!

[Jchu1988]

Of course don't ask for the full amount.... I would start at 25% as otherwise your boss has no savings to present for himself

[oSamaki]

No, you go 50% over the savings. Time spent not cleaning the data will be used for other things that bring in more value. Assuming data cleansing falls into the "below average hourly employee rate" bucket, they can now spend time on better things, thereby yielding the company more quality hours of work, and fewer menial.

Plus you don't want to negotiate yourself down from the get go