Working on large files on local shares - LAN - at 100Mbps can be less than ideal. I'd be careful on moving a business entirely on the cloud unless you are really sure about the type of performance you are going to get.


As to prices, while you have all sorts of ADSL lines for home claiming - and possibly offering - 50 or 60 Mbps downstream at 30-60 Euors/month, here in Italy a business class fiber optics 100Mbps symmetric data link is 3000 (three thousand) euros /month. France and Spain have similar - slightly lower - prices.
I don't know exactly what is being offered by FiOS, but what you describe sounds phenomenal.