They have their place, for certain techniques they are deadly. For example, in one spot I cast out directly in front, then allow the current to pull the floating Rapala around to be parallel to the shore and beneath overhanging willows. I then retrieve it beneath the trees in a spot which is impossible to fish otherwise. Others like to drift a sinking Rapala down a current and over a drop-off to the feeding trout. In such cases they are deadly. In normal, cast upstream and retrieve fishing they are still a worthy lure.
Now, are Rapala worth the $20 asking price? I do not believe they are. There are equally good minnows (storm wildeye) for half the price, then there are the Chinese ones on trademe. They a bit of a gamble but often a minnow the equal of a Rapala can be brought for a few dollars. If I was to spend $20 on a Minnow, I would spend it on a Yo-Zori, they are normally a few dollars cheaper and imo they have a superior action. Only downside to the Yo-Zori is the limited patterns and styles available locally.
So yes, it is worthwhile to have a few minnows.