I would seal around all the lights and other items on the outside. I have seen clearance light lens with a water witness mark inside that is about level with the holes for the wire. When the light fills with water it starts going out the wire hole and in the side of the rig. I have a smooth side rig so others may tell you more about aluminum but they may need more attention to sealing behind something like a marker light because of the irregular surface.
Cheap or expensive, both need to be thoroughly sealed and regular inspections and resealing. I would never trust that a new unit is ok and doesn't need inspection for a year or more. It needs inspection BEFORE you buy it. Months back a guy was on here with a new TC that he picked up and started loading his stuff into and noticed wet cupboards and then went up top to discover a buckled up roof with extensive water damage. It's normal to assume new as being perfect but that is far from true. I repaired a roof on a Rockwood TT that had a damaged membrane from the factory.
So to me, it doesn't matter if it's $10,000 or $120,000 the same marker light or vent cover or poorly sealed screw or aluminum strip will still cause damage.
Some brands will have less damage because they may be built of aluminum and composites like a Livin Lite but they are not $11,000