I believe that what you say is right.  These ministries probably are
OK, even good or outstanding in some cases.  If their leaders prosper,
that is not a sin.

The only problem with this is that it can tend to make those who do not
prosper feel unworthy, unloved by God.
I heard comments about this yesterday on the Calvary network by a
pastor new to me, Scott (did not catch the last name but he's on at
3:30 Mountain Time).  He was talking to a woman who had been wiped out
by "Katrina."  He said no one should make her feet guilty because she
was wiped out; the Lord may have used the wipe-out to teach her some
needed things, but this does not mean He does not love her.  No one
should question her faith just because her life is in a shambles due to
the economic upheaval of Katrina.

Same here.  We got economically injured by another FEMA disaster, the
Los Alamos fire of 2000.  From this we learned a great deal about the
untrustworthiness of helpers, be they governmental, church, or family.
We learned that only Jesus is our true friend.  We needed to learn
this.   And we must not feel guilty because we are now among the
humbled, the powerless.  We too are loved, even if we did not prosper.