Monopoly is a misnomer here. Is Wal-Mart a monopoly?

The parts supply industry is not an industry of monopolies. There are a few large names--Grainger, McMaster-Carr, MSC, Digi-Key--that probably account for 25% of the market, and then a very, very, very long list of names most people have never heard of.

Ironically, Ma & Pa Electronics are frequently the ones with the highest prices. Large distributors like Digi-Key are often less expensive than small local shops.