The way I read this passage, Jesus was speaking to the impossibility of the rich being saved. I don't see it as "if they became poorer they could diminish themselves to the point where it was possible," but rather "in their own power they cannot be saved, the value system that led them to build and maintain their wealth is contrary to the value system of heaven." In the next verse the disciples are shocked and basically say that no one could be saved in this case. Rather than correct them and explain that the rich can be saved after divesting themselves of their riches, Jesus replies instead (paraphrasing), "Yes, you're right. It is impossible, but God can do the impossible." This also leads me to believe Jesus meant "camel," not "rope."