I don't think "rationalist" is a cohesive enough partition to answer a lot of questions about what we/they believe.  There are a full spectrum of opinions about capitalism among those who call themselves rationalists.  

A lot are uncomfortable with the idea of persistent ownership of resources, especially inheritable and especially beyond basic needs.  A lot don't see any better way to avoid tragedies of the commons.  A lot just accept it as the current equilibrium and play the game in order to fund more interesting/important work.  

I personally don't consider myself a rationalist in the community sense, though I do seek to learn about rationality and use it both to refine my goals (and my self-knowledge about them) and my ability to pursue those goals.  I tend to see economic transactions (meaning: legible trade of value, not necessarily currency) as one of the few workable alternatives to raw violence, so I guess I'm in favor of that analytic frame for many decisions.  But it's not the only reasonable frame, and at some scales or for some subsets of partners, other frames (altruism, honor, status) are more accurate.

More narrowly, control of resources is instrumentally valuable for a whole lot of goals, but is not a particularly compelling terminal goal in itself.  Knowing what the profit enables you to do is key to deciding what sacrifices you'll make in pursuit of that profit.