Not sure where the premise is coming from. Are a lot of Canon products expensive? Yes. Do they represent value? A difficult question to answer. But Canon cameras and lenses don't seem overpriced compared to the competition. In fact, many things are cheaper (and yet still better) than comparable competitor products. And given that several camera manufacturers are struggling with profitability, its difficult to argue there is a lot of price gouging or fixing going on. But I'd agree that Canon can sometimes be "tricky" with some of their prices especially when they perceive high demand (eg 5Diii), but I think that helps them offer other things more competitively.
With EF-S lenses, some such as the 10-22 sell second hand with only a small drop in value. Cheap, basic kit lenses don't retain their value (and arguably never have). Its not because they are "bad" lenses. Its simple supply and demand. People are buying second hand because they want a better-than-a-kit-lens lens. Quality lenses and cameras retain their value. The only time when you do see significant drops in value is when a mount becomes orphaned - eg Minolta MC/MD. But even recently, there has been an increase in a prices, which has possible been driven by their compatability with mirrorless cameras.