You'd best remind me what the ending is ! The whole piece is a satire written in ironic terms. Are you ,perchance, an American ? The essay seems to be very well-known there.
I'm not sure the conclusion is any more ironic than the rest of it - the point is, you're supposed to understand that it's not to be taken literally. He's trying to focus attention on the subject by making a suggestion so outrageous that people will be forced to stop and think about what exactly is wrong with it and whether other suggestions put forward on the same subject may also have similar little flaws.
You'd be better off actually reading the essay. Do you think an 18th century church minister would seriously propose cannibalism as a method of defeating poverty? Second paragraph to the end - read it carefully. Swift says if nobody will address the growing problem of poverty, then his suggestion is as good as any as it really would work if implemented.