You said in your request that you want to return the money to those who didn't spend it, so why are you still giving them the starter money, try adding their existing money to the spawn money.
PHP Code:
cs_set_user_money(id, clamp(( cs_get_user_money( id ) + get_pcvar_num(pCvar_ctf_spawnmoney)), get_pcvar_num(pCvar_mp_startmoney), 16000))
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