Very impressive, almost totally right, with a correction in the last 2 lines to fit in with the general theme:
What You See Is Not What You Get
What You Get Is Not What You Want
What You Want Is Not What You Need
What Need Is Not What Is Available
What Is Available Is Not What You See
P.S. The riddle is my creation, inspired by the well known
WYSIWYG = What You See Is What You Get
which doesn't always work as intended.