Compare the memory usage of flex sdk3.5 and sdk4.0.

You can see it directly. Intuitive:
Sdk3.5:
One button with the current memory of 1164 KB
Two buttons, Current memory 1173 KB

Three buttons, Current memory 1178 KB

sdk4.0:

one button, current memory 1736 k

two buttons, the current memory is 1767 kb

three buttons, the current memory is 1787 kb

: sdk3.5 is 1164 K, sdk4.0 is 1736 K, and 572 K is larger.
when a button is added, sdk3.5 is changed to 1173k and 9 K is increased, sdk4.0 changes to 1767 k 31 K is added;
when the first three buttons are added, sdk3.5 is changed to 1178k, increasing by 5 K, sdk4.0 becomes 1787 k 20 k is added.

it can be seen that the spark button is 4 times the original size, which is amazing!