Mr. Dobson purchases a new Honda every other year.First he made a down payment of $12,000 on a vehicle that cost $30,000.The balance is paid in 24 equal monthly payments of $848.00 assuming a 12% APR. When Mr. Dobson makes his last payment, he goes to the dealership and trades in his old car for a new one.The dealership offers him $12,000 on his trade and he purchases a new $30,000 Honda - repeating this same cycle.

Ms. Chastain also purchases the same Honda every other year.She paid $30,000 cash for car.She then makes monthly deposits of $729 in a savings account (paying 3% interest, compounded monthly) so at the end of 24 months, she has $18,000 in the account.The $18,000 plus the $12,000 trade in value of the old car will allow Ms. Chastain to replace the older Honda by paying $30,00 for the new one.

Please explain why Ms. Chastain's deposits into her savings account are smaller than Mr. Dobson's monthly car payments.