Yes,,,for the part alone. But, in many applications, if you consider the extra cost of the other parts that are often rrequired to support the 4051 and the board space, installation, and testing costs involved the difference in cost may start to dim to a mere shadow. There are also some advantages, such as low ON reistance or frequency response, that may increase performance of the product such that an increased cost may be worth it.

I fully agree, Michael. If your PCB is four layer, extra cost of needed extra space can be rather high! Only assume, that for each channel protection circuitry must be added. Then you end up with about 8 resistors and 16 (!) diodes.
Also, for audio applications a signal range of +-7.5V means a drastical decrease of signal to noise ratio (SNR) or headroom. If you can use full signal voltage swing of up to +-15V you gain 6dB in SNR or headroom.
There's another point: The expensiver counter-part often allows a much easier controlling of switch or multiplexer, because many of them are TTL compatible. CD4051 is not TTL compatibel, when you have running it with +12V.
Still another point: Expensiver counter-parts often present a much lower charge injection when changing control signal and much less cross coupling between the different channels. This can be very relevant in some applications.

But: Why not use cheap CD4051, when it's possible?

Bye,
Kai