A distributed audio system can be done a number of different ways and it truly depends on the level of sophistication of your system. I will completely disagree with the poster above who was talking about lousy sound or failure as a properly designed system will last for decades without any issue at all if you have decent gear.
12 zones typically would mean two 12 channel amplifiers for discrete amplification, which will run from $1,200 to $2,000 MSRP for new amplifiers, plus your audio distribution unit (preamp), controller, and keypads.
Keypads typically take a piece of CAT-5 and speakers will typically be run with 14 gauge speaker cabling.
I would plan on about $120 for labor and wiring per speaker location plus another $70-$90 per location for the keypad.
That would include cutting in speakers, putting in back boxes for keypads, terminating keypads, and all wiring.
Keypads would be per unit pricing.
Speakers, ditto.
Programming will depend on the complexity of the keypads and the sources.
As a full example of somethign I would do with new gear:
2 amps: $1,500 (B-stock)
Crestron Controller (MC2W) - $400
Crestron Power Supply: $100
Crestron 12 button keypads (12): $1,200
Crestron PAD8 preamp (2): $1,200
Speakers (your choice): About $100 pair (12 pairs): $1,200
About 1,000 feet of speaker cabling and CAT-5: $400
Misc Materials: $100
Labor: About $3500 total
Turnkey system with up to 6 individual sources available to each of 12 rooms at your choosing.
Total: (about) - $9,500 - $10,000 for a fully installed system in NEW construction (pre-drywall)
But, home size greatly impacts this as would a decision to change speakers to something nicer/cheaper. Inexpensive is $100 pair of speakers which work nicely for room/house music, but some Sonance 622TR speakers which are better will be $150 or so a pair while cheaper ones can be done for under $80 a pair and still sound perfectly fine.
I've used similar in my home and have had zero issues with my distributed audio for the last five years. One of the big things that can be done is going to a nicer amplifier setup, which costs a bit more, but can be more reliable long term.