Where to start?
First, "depending upon what anyone else says will get you into a bad situation" is amply demonstrated.
Second, the ratios are not "flawed". They are what they are, computed from the data available. The average may well not apply to any particular transaction, as virtually all means of most data sets are not replicated by any individual data element, and of course there are other significant variables affecting any given transaction which were not available to me to take into account. The range of values indicates that. The appropriate caveats to the analysis were noted.
Third, data, or, equivalently, information, including actual experiences in a given situation, and their analysis, about boat purchase transactions, or use of navigation charts, or GPS or compass readings, or engineering data on the strength of materials, or, well, you name it, is the only way I know of, other than trusting to luck and prayer, to understand and make better decisions when choices are available.