The Medrash says that it says by Yetzias Mitzrayim "V'Lakachtem" you should take a piece of "Eizov", grass and dip it into the blood of the Korban Pesach. The medrash then says that the eizov costs but a few pennies yet it earned us the reward of the wealth of Mitzrayim, first when we left, then again at the Yam Suf, and then again from Sichon and Og and all the nations that lived in Eretz Yisroel.
By Lulav and esrog it also says "V'Lakachtem". A good Lulav and Esrog which can cost a small fortune will return a far greater reward then the very appealing reward we received for the little blades of grass. If you spent a lot of money on your Arba Minim you may be smiling now and justifiably so!