Hello Brendan,
We found the difference in re-sale value with Jayco's, although better than other Australian made vans was offset to a large degree by the quality of the cupboards and fittings. If you have a look at Nova, Island Star, Kingdom vans, you will quickly see what I am talking about.
In particular, real timber, not laminates used on cupboard doors, one piece fibreglass shower enclosures as opposed to multi panel shower enclosures (Jayco/Avan and others)
So what I am trying to say here is, brands other than Jayco do tend to depreciate quicker than Jayco, but for someone looking for vans on the second hand market other than Jayco, this is a huge plus because in our case, the difference in price between our 4 year old van and a new one was +$30K.
We found looking at second hand vans an eye opener insomuch that some brands looked quite dated and did not age well after 5 years. So whether you are in the market for a new van or an old van, a walk through the second hand lot gives you a great insight into what a new van by any manufacturer will look like 5 years down the track.
Hope this helps your decision.
Cheers, Marschy