Cogent Bandwidth Question...

[Telemachus]

I'm hunting down a hosting solution for someone and though they don't need anything overly large transfer-wise just yet (3tb/month is what they have me shooting to start off with for and that's easy enough), they're very concerned about rapid growth and the bandwidth it may require.  After reviewing the options and getting some quotes, I see there are two choices, either go with a reliable and realistic host which has monthly limits per plan but provides real tier one bandwidth, or accept the risks inherent in something allegedly unmetered and hope for the best.  I know my obvious skepticism toward the latter makes it sound like I've already decided, but I'm too naive on the matter to know if all the dreadful things I've heard about Cogent provided bandwidth, and even worse the companies which offer it and far oversell their true capacity, are true, and/or whether it may not be that bad an option under certain circumstances.  Thanks in advance if anybody well versed in the needs of commercial sites has some opinions and/or advice to offer.