First, I have no first-hand knowledge, mamahills, but I can empathize with trying to generate some motivation to pull a few more essays out of the hat at this point. That said (as one who doesn’t have to do the motivating 
I think the ROI is sound. Sapphire Leadership seems to be a well-regarded, delineating factor in Smeal and is noted when reviewing linked in, resumes, etc. post PSU. Are there also additional/early entry classes offered? Did he also apply to Schreyer and could he possibly “retread” some of those ideas? The fact that they contacted him gives pause too, doesn’t it?
Of course, you know your son’s workload at this point; for me, the few hours invested may generate some really positive/unique avenues/opportunities. This thread looked pretty good http://talk.collegeconfidential.com/penn-state-university-park/1276215-sapphire-leadership-program.html
Hopefully, a student can respond. Good luck!