Tile generation wasn't THAT bad. We only cover Colorado and Wyoming, and generating the tiles for those at the zoom levels 5-18 takes around 7 hours to pre-render (using "render_list_geo.pl"). The end result is around 25GB of rendered meta-tiles.
Much better than the NAIP aerial imagery, which takes around 3TB for the source data, 280GB for the resulting tiles, and around a full day to generate.
Yes it wasn't bad for a single area (we cover only Greece and it was quick and easy for such a small country). However I couldn't imagine of the resources needed to cover the whole world!
Much better than the NAIP aerial imagery, which takes around 3TB for the source data, 280GB for the resulting tiles, and around a full day to generate.