Depends on how you get them;
SUB 75k for a 99$ card and 4k spend = 200$ cost /75000 = 0.3 cpm
AA miles are always the most expensive from spend = lost cash 2.625c each
Bask bank - 3 miles +3x0.42c = 1.26c = 1$ kept for 1 yr = 5.25c in T bills; so 3 miles = 4c = 1.3c real pretax cost
Valuation does not equal cost
(And your Bask bank calculations are off - you get 2.5 miles per dollar and the $0.42 per mile is the taxable part - not their cost)