The ending of Perfume: The Story of a Murderer is just as bizarre and unique as the rest of the story is. To have Grenoille concoct his own death in such a painful and flashy way surely ended the novel on a memorable note. In doing so, Grenoille gives admittance to several things. First, his talent is beyond comprehension--to develop a perfume that would drive people out of their rational minds, to commit cannibalism, is simply unbelievable. Secondly, that that immense talent was dangerous, evil, and uncontrollabe, not only by him, but by anyone who came into contact with its full force. Thirdly, Grenoille admits that he is miserable, and that the perfume has given him all that he could ever get out of it, and can no longer do him any good. His experience with the crowded town and the orgiastic chaos that he caused to erupt was the pinnacle of his life, and there was nothing left to do--after that, his gift was just a burden, and he had no purpose in living anymore.
The irony in the statement at the end is multi-layered. On a symbolic level, to take Grenoille out of the world is an act of love for everyone else who might have been endangered by his obsession with perfect scent. To kill him is to love life, because he destroyed it. Also, Grenoille wanted to die, and for the first time in his life, people did something for him--they showed him kindness by helping him to die. It could be seen as an act of love for him. On a more literal level, his smell was so enticing that they literally loved him as they consumed him, in the way that we love a good steak. It sounds morbid, but there you have it. The irony in all of these interpretations is that in "loving" him, they brutally murdered him. That is not quite what one would expect.
I hope that those thoughts helped; good luck!
I think mrs-campbell said it right. It's also the fact that if we love something to much we end up destroying it. It's like everything else that is done in excess. Too much is bad.