Retail price means nothing - just like double glasing. Remember there will be VAT, RFL and Reg Fee on the 'bottom' price.
I see their current model is making way for the NV400 so if you don't mind an old model new van, then this is a good time to look. Of course you will find your trade-in price further down the line will also refect it being one more model behind.
The Nissan was based on the Renault Master/Vauxhall Mavano which wasn't a popular van.
Spruce