The price per night varies from van to van and is set by the van owner. The base price is the price of the van on the cheapest night of the year - for example a mid week night in February (off-season), this base price changes dependent on the date and season you are booking in. Per night prices are more expensive over weekends, bank holidays and during summer months (High Season).
If in doubt, use the calendar on your chosen van to see the exact price for those dates. If no dates are selected, it will show today's rate.