Of course it's more expensive. You pay for the convenience.
The bleach is standard pot ferri. I use the bleach very dilute, and bleach for a very brief period of time, and then use the 'yellow' mix to get those golden highlights. Just this treatment alone is quite beautiful and adds real depth to a photograph. Then I usually follow up with Harman selenium toner, and sometimes I start from the beginning again with the bleach and bleach again, and repeat until I have what I want.
You can do all of that with a toner you mix yourself, and the results will be just as good. But as Brian says, you will have to mix it yourself, which assumes you have an accurate scale, and the rest of the equipment (and knowledge) to do that safely.