Yes, the C64 had a sound chip that gave them the capability to handle multiple streams of audio easily. So they leveraged that into 300-baud data storage on cassette tapes.

In that day, that wasn't bad. After all, those of us using much more expensive minicomputers were storing our programs on punched paper tape on ASR-33's, and that happened at only 110 baud. 

The C64 was, if my memory serves, the most-produced personal computer of that time. They made millions and millions of them in an age where most computers would be deliriously happy to ship only one million.  I think they got the cost of goods on the C64 down under $30 each, and sold them for a few hundred bucks.