Keep in mind that the premium also goes up every year (the same as the pension COLA) and will be paid up only when you've made 30 years of payments and when you're also older than age 70 (both have to happen).
One problem is that life insurance is... insurance while SBP is a govt-subsidized inflation-adjusted annuity. You may need one for a limited time or neither ever... especially if your spouse has their own assets.
To make the discussion even more treacherous, many military spouses feel that they've "earned" the right to your SBP by virtue of sacrificing their career human capital earnings potential to follow your career at the whim of the military assignment officers. Not only is that decision in the hands of your spouse, but they're absolutely correct in this (emotional) behavioral financial psychology attitude.
The most balanced discussion (and financial analysis) that I've seen is Forrest Baumhover's new eBook. This grew out of his posts on MilitaryInTransition.com and I took my turn at editing it:
https://www.amazon.com/Military-Transitions-Guide-Survivor-Benefit-ebook/dp/B01EPB5H1Q/ref=sr_1_1
Personally, my spouse and I both declined each others' SBP since we both have our own military pensions and other assets... and we'd rather spend the 6.5% on each other while we're alive. In the same logic we also do not carry life insurance.
I plan to take Social Security at age 62 and invest it in a passively-managed equity index fund with low expense ratios. I won't need to touch it. It's part of my long-term care self-insurance fund that I hope I never need to tap.
My spouse has Ashkenazism genes and will likely outlive her centenarian grandparents, so she's going to wait on SS until age 70.