In evaluating homebrew races for how balanced they are, you often have to compare features against each other.
One recommended approach that has been used several times for this is the Detect Balance spreadsheet, which provides point values for various features to make them comparable and enable calculating an overall value of a given race, so it can be compared against the total of other, official races.
My impression is that the spreadsheet is well thought out, and this is an effective way to do such evaluation. (Although one could argue that any point-buy system will eventually end up broken, as the fixed point values fail to capture the sometimes substantial synergies between options -- think of flying with ranged combat). Of course it can not provide any official evaluation, but I think this is fine, given we are talking homebrew.
However, the spreadsheet does not provide supporting arguments for the values it came up with.
There are questions for evaluating the relative value of features, for example for armor proficiencies, half-feats, resistance to damage, low-level spells, spell ladders like Infernal Legacy, but I could not find anything for darkvision, which is very common.
The DBS gives a value of standard darkvision 60 feet as 3 points, on par with the value of a free choice of skill proficiency for a single skill.
Is there a way to support this equivalence?