Now you are saying that you don't trust Wizard to return the Bitcoin. Whether it goes up or down in dollar price you get the same amount of Bitcoin back if the person taking up the challenge fails. If the person succeeds they get 5k cash and you get the difference in BTC back if the price of Bitcoin rises during the escrow period. The only one taking a risk is the one trusting you to pay the dollar difference if Bitcoin declines.
Plus if there's any shenanigans with the bag holder running away Axel has stated he will cover your loss. That is why he was willing to post money too. It's all about proving funds to cover the challenge.