The only problem is, scripture actually does speak of God's Kingdom in terms of material blessing!!!
Certainly more than merely wealth and health, but definitely including health and wealth.
The prosperity preachers have that part right; God does indeed want you to 'overcome' and to erase all tears, to provide food and drink at no cost, etc.
The problem is not in the preaching of a prosperity from God but in an inaccurate eschatology (forgetting the Kingdom is both now and not yet), in an awkward theology (portraying a God who both condemns greed and rewards it), in a short sighted perspective on suffering (unaware of the fruit of God's discipline), and in a skewed understanding of discipleship and spiritual formation (our desires are not in need of transformation, and can simply be pursued 'as is')