We have an 8 x 20 foot space and used Nu-Heat. Seems like it was about $1,200, would have to pull the invoice.
If you live in a cold climate as we do it is more than worth every penny. We hated our cold tile floors for 15 years and vowed we would have heat under our travertine floor even if we did nothing else. What a treat it is this winter. If you live in a warm climate, not quite as essential for comfort.

You'll never regret it once installed, BUT just don't get "Warm Tiles". It only heats the tiles to a maximum of 90 degrees -- which although it sounds like it is hot, really isn't. This is one of the major disappointments of our new build. Whichever brand you get, research it well and make sure it gets hot enough to suit you. We have another brand of bathroom tile warmer installed at our other house (sorry, I can't remember the brand name), and it gets plenty hot enough.

If you live in a cool environment it is totally worth it! $2k sounds a little high though? You will not enjoy your marble floors unless they are heated...

We just DIY'd under floor heating in a new master bath. It was less than $500. The bathroom isn't complete yet so we just tested it. The tiles didn't get as hot as I thought they would but I could feel warmth through my slippers. We will have to play with the temp setting to get it right.

I would look in the price more... but do it. I once stayed in a house where there was underfloor heating in everyroom. It was so comfortable. Cold floors are no fun.

amytc, is this to go onto a concrete slab or a wood subfloor or something else?

In the installation that nclakehouse describes, I'll bet the heat coils are in direct contact with a thick concrete slab. This makes a difference.

amytc, do you know enough about the building envelope to describe it? And the insulation?

To get an installation that will satisfy you beyond your wildest expectations, you have to know these elements and manage to create less thermal bridging and more thermal isolation. Read wikipedia on thermal insulation.

It IS entirely possible for in-floor heat to be sufficient for a building's heating requirements. (But it's not easy to educate DIY about this.) It is also possible for in-floor heat to be sufficient for any one room in your house. Not likely in the average house though, and that is because people don't understand the specific steps to take to create a heat- insulated environment.

I have Nu-heat radiant heat under my master bath tile floor and love it, but more importantly the cat adores it. I would get it again in a heartbeat. We paid $1500 for installation & materials.

We have a Warmly Yours electric heating mat under our tile, and it was of the order of $400 when we got it 4 years ago. Definitely worth it.

We just installed our Warmly Yours heated floor mat under our travertine in October. What a difference it makes!!! We have knee walls covered in the same travertine and they are extremely cold to the touch, so I can just imagine how cold the floor would be without the heated floor. We never turn ours above 83 degrees and it's warm enough to feel very comfortable. I believe it was about $650 for the mat and thermostat for a 42" wide x 10 ft. long area.

Davidro1, no, our installation is not on a concrete slab --- there is a wood subfloor -- and the system was installed in accordance with manufacturer guidelines.

The system installed in our Atlanta home back in 1996 was by "Warm Touch". I much prefer it to the "Warm Tiles" system at our lake house, although I'm sure there are other equally good brands.