I was asked by a colleague with 730 MQM - is it worth shooting for lifetime Silver?
He has his own company - can get enough people to spend on his card

These were my calculations for his family
Each DL member can get 105k more MQM on their cards this year (each has done 30k for the waiver)
2 people spending 210k will get 105k MQM each (and for DM status spend 220k - just 10k more)
His son can do 120k spend = 60k more MQM
total 210+60= 270k MQM for lifetime Silver

Cost of spend of 540k is 14175$ Lost cash
Cost of 3 new DR cards = $1500 (but can downgrade next year) so perhaps 600$
Value of DL miles 1.15c x540 = $6210
Real cost in cash lost = 16000-6000 = about 9-10k (not counting 500$ a yr in lost interest) - for what?
Ability to select a better seat @24hr ?
Free bags - available with a DL Gold card
I told him not worth it

For 950k MQM I would strongly urge him to do it
for 1900k to get 2M it may be well worth it at 200k spend = 3000$ real cost
For 3700 MQM to get to 4MM and lifetime platinum with 300 MQM this year, it may just may be worth the money of 10k lost but not for lifetime silver

540k spend will get all 3 of them to AA EXP - but best used on cash back