First I've heard of the suggestion that the cost of a car should be 50% of annual pay. To me that's insane, but then again I view my car as an appliance[0].
For a coherent analysis, you should use the median income of two earner households. Two people where one makes $75K and the other makes $50K equals a household of $125K.
And it seems obviously extravagant to me for a middle class family to have two new cars. One maybe, but two? But even so, by the formula, the family can afford two $30K cars.
in 2005, the last actual data I could find that lists 2 income households, the median income was $75,293, assuming that income kept pace with inflation that would be $98,562 today not 125K,
Such a family would not want to spend more than 49K total on their cars. so that is 1 car for 49K or 2 for 24K
[0] https://oppositelock.kinja.com/i-used-to-take-it-as-a-given-...