I liked much your reasoning on “affordable”. I also call out relative price: a price that reflect percentage respect to own financial situation. I m doing some analysis on prices for houses, the same could be applied to fines for breaking traffic rules, the same for primary needs as food: a fixed price that is assume to be qualitatively (as perception) “low” or “high” can quantitatively hit as devastating (in condition of severe relative poverty) or negligible (in condition of high relative wealth). Culture is shaped by wealth distribution (curve of capital ownership), and so they do perception of fairness and measures adopted to embody democratic choices.