Monopoly does not mean bad product. It means having nearly ALL the market share.
In actuality, there are far more heinous monopolies created by way of gov't regulation than in any other way. Massive regulation is an advantage to bigger dominant companies because it creates large barriers to entry into a market. Some companies lobby for more regulations because it helps them to ensure that others cannot enter the market.
Otherwise, smaller more nimble companies would come along and undercut the dominant company. This is how capitalism is meant to work but in these days or massive government interference in the economy things don't work this way anymore.
Look at the wal-mart strategy if you want an example. While there's competition, prices are low (sometimes even running at a loss). Once the competition goes out of business and you have a local monopoly? Crank those prices, extract as much profit as you can from your now-captive market.
Most markets have significant barriers to entry even when the government isn't involved at all.
Do you have a few examples of Wal-mart changing a product's price from low to gouging?
I don't go to Wal-mart a whole lot, but do drop in for this and that and I don't think I've ever seen anything that was notably over-priced.
But what I have heard about is them putting the screws on suppliers. In a world where they have less of a monopoly a supplier could say, "Screw you... we're not going to move our manufacturing to China to save twenty five cents per doodad", but now suppliers largely do what Walmart says to do.
It was the same with Microsoft 15 years ago, though AFAICT Google are nowhere near as nasty as they were.