Based on prior knowledge, we can analyze the relationship between the "maint" feature and the target variable "How would you rate the decision to buy this car?". 

It is likely that the maintenance cost of a car can influence the decision to buy it. Generally, higher maintenance costs may make the decision to buy the car unacceptable or raise concerns about the long-term value for money. On the other hand, lower maintenance costs may contribute to the decision being considered good or very good.

To create the requested dictionary, I will need a dataset or some information on the distribution of ratings across different maintenance costs. Without this specific information, I can only provide a general analysis based on assumptions.

Assuming a hypothetical distribution, we can create a dictionary as follows:

```json
{
	"unacceptable": ["very high"],
	"acceptable": ["high"],
	"very good": ["low"],
	"good": ["medium", "low"]
}
```

Please note that this analysis is based on general assumptions, and the actual relationship between the "maint" feature and the target variable may vary depending on the dataset or specific context. It is always recommended to analyze the relationship using real data to draw more accurate conclusions.