It must be a Bernese Mountain Dog thing. Ours is a mix Bernese and Springer Spaniel (and a whole host of lesser contributors) and he has only jumped into the van twice in his life. We have to pick him up, but at 75 lbs is a little more manageable than yours.
Having said that, we bought a nice ramp and our dog also gave us the "are you bleeping serious" look. Sooooo, if you are looking for a nice ramp, I can offer it to you at a discount over new (and it is basically new and unfortunately never used) if you are in the SF Bay area (I'm in the east bay).
Oreo ... my lazy butt dog (but a great dog!)