There's 2 ways to look at this. On one hand, if they're diligent to their work and they are successful, who's to say they shouldn't live the life that they want to live. Also it could serve as a testimony that extravagant lifestyle are possible and dreams are attainable... But on the other hand, I'm sure many would prefer to see a pastor living a more modest life, as to appear grounded and humble. You would think that a pastor would want to contribute the fortunes to the needy members of the congregation, or donate to starving children across the world instead of buying a new aventador. An excessively flamboyant lifestyle does show glimpses of pride and arrogance, in my opinion. At the end of the day they're human and we cant force them to conform to our ideals of how a pastor should live. If they earn the money legitimately, it's theirs to spend.
Reminds me of a story that my friend told me about a pastor of a fairly large church here in Alabama. The church is very well known in the city, as is the pastor. One day he was car shopping with someone and a Honda Accord caught his eye. The person that he was with basically scoffed at the modest selection and said something to the effect of "You're a big time pastor, you need to be driving something like this..." and gestured towards a new 7 series. The pastor responded "As a pastor, how would I look pulling up in an $80,000 car, and I've got people in my congregation that can't pay their light bill." I gained tons of respect for him after hearing that. The church is in a low i come neighborhood also.
The grey area is basically whether you consider a church a business or not.