The lump-sum fee is just an example number. It could be less for smaller rentals but the point is still there. You need to force new hosts to "prove" they're going to be honest and have a penalty for those who aren't honest. This same concept is used in the cryptocurrency world where you need people to have trust. One example I can point to is Storj where they withhold earnings from people who don't perform per the agreed terms (in this case keeping your storage node running 24/7).
It is okay if certain people are excluded because you only want people hosting that are SERIOUS about doing it. If you can't do the surety bond then you simply aren't ready to be a host. It really is that simple.
