this site doesn't do 50% JS they quote 100% and straight life - you can interpolate those to get a reasonable estimate of what it would take to purchase the $2400 a month immediate annuity - I was getting something over $600K to purchase an equivalent annuity using 57M/53F an immediate start date - did the packet quote a
relative value to the immediate annuity?
https://www.immediateannuities.com/information/annuity-rates-step-1.html
I interpolated a $403k premium today as a $24,441/year 50% joint life fixed annuity starting in 8 years at 65.
$403k premium, 8 year deferral, 57yo/M, 53 yo/F in MO.
100% joint life = $1,858/month, 57yo/M = $2,406/month, 53yo/F = $2,025/month
[($2,406+$2,025)/2 + $1,858]/2 = $2,036.75/month for 50% joint life or $24.441/yr vs $28,416 provided from plan.
I interpolated a $487k premium today as a $23,037/year 50% joint life fixed annuity starting at 65.
$403k premium, no deferral, 65yo/M, 61 yo/F in MO.
100% joint life = $1,764/month, 65yo/M = $2,215/month, 61yo/F = $1,936/month
[($2,215+$1,936)/2 + $1,764]/2 = $1,919.75/month or $23,037/yr vs $28,416 provided from plan.
So it looks like the plan is providing a more than fair benefit in relation to the lump sum.