Taken further we find the problem of bottlenecked economic throughput or market participation due to the poor's access to capital. Markets thrive on distributed inputs to arrive at a consensus on value - the more participants participating, the more throughput of information being supplied to our markets. More participants is more information which allows healthier markets which provides more opportunities for growth.

So what's the cost of a loan or other financial products? Of course there's utility in providing upfront capital in exchange for time-spread payments and interest (buy the $200 boots today), but what of the macro-cost of decreased market participation for the duration of the payments? The loan payments with interest is money that could've been used by an individual participating in the market that is instead piped to the financing provider who, by definition, is already richer.

Given the rich, or a rich organization, has different buying habits and participation in the markets (different perspective = different information), how much economic flow, throughput, and growth are we losing from financial mechanisms which go from poor -> rich? In this sense wealth concentration is a problem of bottle-necking economic potential by depriving our markets of participants and diverse perspectives.