> It's worth $1000 but is otherwise in fine condition.
You need to calculate if the cost of 4 tyres plus any future maintenance costs (and the time that is going to be lost in the future for maintenance) exceeds the cost of a new car minus the cars current value.
Opportunity costs and value brought by a new car is hard to calculate, yes, but the motto is: if you like the car to spend 1000 on it, just do it. E.g. My car is 15 years old, while I can afford a brand new one, I don't, because I love it :)
You need to calculate if the cost of 4 tyres plus any future maintenance costs (and the time that is going to be lost in the future for maintenance) exceeds the cost of a new car minus the cars current value.
Opportunity costs and value brought by a new car is hard to calculate, yes, but the motto is: if you like the car to spend 1000 on it, just do it. E.g. My car is 15 years old, while I can afford a brand new one, I don't, because I love it :)