Ski parking Val thorens

Hi all
I am currently exploring the options for parking in various ski resorts. I am hoping to visit Val thorens with a vw transporter. As there are no nearby campsites, I'm looking at parking. They have uncovered parking for motorhome with no facilities for €170 per week or covered parking for vehicles under 2.20 @ €70 per week. Since there are no facilities at the motorhome car park, why pay an extra €100? Do you think I could get away with sleeping in my van in the covered car park? thanks