Well, I don't have any empirical evidence other than life observations - but rationally when you think about it appearance should become less of a decisive factor as women approach the 'family age'.
E.g. when people are in their 20-25s long term commitment is not something that people think about that actively and as such, attractiveness (physical) easily becomes the main driver when choosing a partner.
On the other hand, once you reach your 30s and long terms commitment (the biological clock / family) becomes a key concern, where other factors such as career / financial stability / responsibility / being a 'good' family man gains a lot of value as a whole (an attractive woman probably doesn't want to commit herself to someone who's very attractive but a bum) - i.e. she'd rather go for a guy that's a 6 in looks and a 9 in 'long term family factors' rather than the opposite.
So, I don't see it as totally unreasonable that the relative weighting when it comes to attraction factors change over time, e.g. 'looks' becomes less important (but not unimportant).
The majority of men (at least that I know), who have high incomes and are 'stable guys' have pretty wives (note majority), regardless to if they're average looking.