I work at Culture Amp and was once team lead of the Design System team.
Its not hard to justify the team. If 4 front end engineers in a design system team can solve some common problems (writing components, improving accessibility of existing components, writing docs, answering technical questions etc) in a way that makes 40 product facing front end engineers more effective than 44 who don't have access to the team... then the team is a net positive.
At our scale we'd need to give a 10% improvement in efficiency to the product engineers. Both the engineers in product teams, and the various levels of leadership, have seen enough to believe we're making at least that much of a difference. Like almost any other company... measuring that accurately is a nightmare (and would require a significantly larger team just to measure ) but its a safe enough bet that we continue to invest in it.
The problem, with something like a Design System and many other aspects of organizational management, is that efficiency measuring tends to ignore the overhead, the death by a 1000 papercuts, and only focuses on the sweet points.
Its not hard to justify the team. If 4 front end engineers in a design system team can solve some common problems (writing components, improving accessibility of existing components, writing docs, answering technical questions etc) in a way that makes 40 product facing front end engineers more effective than 44 who don't have access to the team... then the team is a net positive.
At our scale we'd need to give a 10% improvement in efficiency to the product engineers. Both the engineers in product teams, and the various levels of leadership, have seen enough to believe we're making at least that much of a difference. Like almost any other company... measuring that accurately is a nightmare (and would require a significantly larger team just to measure ) but its a safe enough bet that we continue to invest in it.