Know the whole "software developers are bad at time budgeting / estimation" (experientially-validated) cliché? Well, have you ever seen a shared resource that collects and surfaces costs? Seems like that may be related.
Revealing what's hidden. We share lots of aspects of implementing things (case reports, blog posts, etc) but I feel like I rarely see aggregations. Admittedly it's hard to compare but its still a resource I'd like to see.