Are wealthy preacher evidence against the truth of the Christian message? Is it OK for certain preachers to have big incomes? Is it OK for any Christian to have a large income? What should our attitude be toward this? 
Yes, there are certainly some greedy preachers who do not accurately represent what faith in Christ looks like. But... are you and I any better? The same people-pleasing, self-gratifying approach that leads Christian authors and speakers astray is the same thing that leads you and I astray. If we are going to call these others to account, which needs to be done, then we also need to call ourselves to account.