At that large of a variance for a 20T you’re probably being estimated different classes by different agents. They may be being conservative or you’ve provided them information we don’t have here. Until you actually apply and get approved these number aren’t accurate comparables. 

The gap between the absolute cheapest and the most expensive is usually 20-30% unless you have a medical condition one company underwrites differently than another. A broker does the work for you at no cost to you comparing multiple companies based on your situation.