The number above is probably pretty close, but there's a misconception that WebKit is only a tiny fraction of Safari: it's not. Most of the manpower and work goes into it; Safari is just chrome around it (albeit chrome that does take a reasonable amount of work to make…just not as much as it does to support JavaScript and WebAssembly VMs, page styling, rendering, WebGL and WebGPU, networking, tracking prevention, and maintaining support for the the ever-growing list of web standards WebKit supports and participating in discussions on shaping them). Safari is just one of the clients of WebKit.
