6mo vacant policy over 2x 1 yr primary residence policy

We closed on another house, and the old house will be vacant (with some work) until it sells.

What surprised me is that the primary residence HO policy was about $2500 for 1 yr. All vacant policy quotes from an agent to insure that same property are about $3000 for 6 months, or well over 2x the primary residence policy cost on a monthly basis.

Is this expected? should I check with another agent?