Good question Feh.
In a broad economic sense, suicides are a help, so they're not selfish. People who commit suicide are (temporarily or chronically, for whatever reason/s) mentally ill. They're mis-functioning members of society who remove themselves from it. They free up a job (if employed), and relieve the state from paying unemployment if they're not. They also relieve the state from having to pay for them in their old age thru pension, health insurance, residency, etc. If they're under a doctor's care for physical or mental problems, they've freed-up a bit of space for someone else. Sometimes they free-up housing for someone else.
In a microscopically narrow sense, if they have close family members then the negative impact on them personally is really the only drawback.
They're also not selfish because, unlike breeders, they're unlikely to go around bullying other people to commit suicide too.
In a broad ecological sense, adding more people to an already overflowing seething pot of humanity is incredibly selfish. Economically, getting new people to replace SOME dead people is a good thing, but the globe's population passed that point about 50 years ago. If advanced aliens ever encounter the Earth, they'll probably be tempted to do some spraying, lay some traps, put out irresistable trays of poison to knock our numbers back down by a couple billion.
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"The death of creativity is a pram in the hallway"
- Cyril Connolly