Branded presence at the festival can cost anywhere from $108,000 for a brunch to $4 million for a blowout concert, per a sales deck and interviews.

Splashy installations also give an impression of prosperity and success to prospective clients and talent. And sending employees to Cannes can pay dividends in terms of retention and goodwill.

Still, all of these measures are unspecific at best, particularly in a shaky economy that’s caused marketing budget cutbacks and layoffs. For agencies, the investment and how they’re tracking performance is especially questionable, said Greg Paull, co-founder and partner of consultancy R3.

Read full article on AdAge here.