We spent a lot of time -- like A LOT of time -- on tiny things like how some countries use single or double quotations (e.g. guillemets « », or bottom quotes like „hello"), or how some countries use . and , differently for writing numbers ($1,999.99 vs 1.999,99).

Seems dead-simple, but multiply that out across many different countries, regulations, taxes, and systems and we ended up with a core team of roughly 15 hammering away at this; factor in different stakeholders, managers, contractors, vendors, etc. and maybe 150 people worked to fix these otherwise simplistic issues.