The buyout that caught my attention this week involved fintech wealth management firm Wealthfront. UBS — the largest private bank globally — bought it for $1.4 billion.  The acquisition got plenty of press. Several articles focused on the low buyout price. For venture capital (VC) firms in particular, $1 billion just doesn’t do it anymore. VC funds have grown very large and expensive. These days, they need multibillion-dollar liquidity events to make…