Risk of suicide actually rises after SRS. It's not just "these people would have killed themselves anyway" - they are actually
more likely to kill themselves after having their genitals butchered. Complications include permanently losing the ability to orgasm (or even pee, in some cases), repeated antibiotic-resistant infections, needing a colostomy, edema, wound separation, necrosis, kidney damage, stool leakage, nerve damage, and many more. If you ended up pooping in a bag for the rest of your life because some subreddit made you believe that the procedure that caused you to have to poop in a bag was the way to true happiness, you'd probably be more likely to kill yourself. Yes, psychological comorbidities make suicide significantly more likely, even in trannies who haven't paid tens of thousands of dollars to filet the most delicate parts of their anatomy like a fresh-caught trout, but they aren't the full picture.
Re: breast implants - unlike SRS, I'm only familiar with a few of the possible complications, like capsular contraction and the fact that some implants actually grow mold inside them and make you chronically ill. Those alone sound awful enough that it might make someone not want to live.
Edit: It isn't cosmetic surgery, but LASIK also elevates suicide risk substantially because of post-surgery complications. In general, you just shouldn't mess with certain parts of your body, even if you're mentally and physically healthy.