^^^Here is a couple different scenarios that could play out with different truck purchases.
He could buy the new $72k truck and flip it every year for say $9000.
He could buy that $72k truck and keep it 10 years sell it for $36 and buy a new one again for $95k. As well he could put $7600 per year into a tax sheltered savings plan.
He could buy a 10 year old Duramax with 100,000 miles on it for 22000 and in 10 years sell it for 2000 and buy a 10 year old lariat for 36k and put $13k per year into savings.
Option 1. After 10 years he has a $95000 truck in his driveway and it has cost him 192000 to get there.(I'm saying about $30k in interest)
Option 2 After 10 years he has a $95k truck in his driveway and $106,000 in savings (assuming a 6% return) it has cost him 72+29+15 (interest) + $76k savings = $192k.
Option 3 After 10 years he has a 10 year old $36,000 truck in his driveway and $182,000 accumulated in a tax sheltered savings plan. It has cost him $22k (10 year old Duramax) + 36 (10 year old Lariat) -$2k (salvage value on the 20 year old Duramax) + $3k (interest) and $3k (repairs) + $130k (savings)= $192k to get there.
If he continued to follow option 3 for the next 20 years he could even reduce his savings contribution to $10k per year and he would still have $1,000,000 in his bank account at retirement.
