Patagonia was definitely the highlight of our trip (which included Buenos Aires and Iguazu). We did this part with a tour which made for a more expensive way to travel but took the hassle of planning away as we left it rather late. So I don't have a lot of details of prices.
We spent 4 nights at El Chalten, the Hosteria Posada Lunajuim was very comfortable with friendly staff, it's family-run. I think the cost there is around US$115 for a double. The scenery was beautiful, we were lucky with the weather and saw the mountains with clear blue sky for most of the time. Good hiking with many relatively flat trails but they're long unless you camp (camp sites are free). The walk from Hosteria El Pilar to Laguna de Los Tres and back to El Chalten via Laguna Capri is stunning, 22km or so.
The Perito Moreno glacier has formed a land bridge and dammed the Brazo Rico for the last couple of months, the difference in water level behind the dam is evident. If anyone is there when the dam collapses, please post your photos on this site! I will patiently wait the year or two it could take. We did the minitrekking which was interesting but disappointingly short. We spoke to other travellers who hiked on the Grey Glacier (Torres del Paine) which has an ice climbing option with pick axes (US$120 or so) or who went walking on the Viedma Glacier with its ice tunnel (near Chalten, I think about US$80) and who raved about those, so if you're travelling to those areas and interested in walking on a glacier, they might be better options than walking on Perito Moreno which is pretty crowded and doesn't offer anything so exciting. We saw or heard plenty of icebergs calving, probably 10 or so in an hour while we had lunch. One was a big event, the others smaller. It drizzled most of the day but apparently that makes it more likely that icebergs will calve and makes the ice appear very blue. It also keeps the crowds away!
Calafate has lots of artesanal ice cream parlours and chocolate shops. It's lucky we weren't staying there for longer, or we would have gained weight despite all the walking we did. Calafate berry ice cream is very purple but delicious. We ate at La Posta restaurant at the Hotel Posada Los Alamos, our favourite meal after the BoBo in BA, and La Tablita which has good Patagonian lamb and steaks. Hotel Shehuen is a little way out of town but has a lovely view of Lago Argentino from most rooms (very comfortable) and a swimming pool, and again friendly staff.
Undoubtedly the best part of our trip was Torres del Paine National Park. We took a boat from Puerto Natales up the Seno Ultima Esperanza to the Balmaceda and Serrano Glaciers. We passed a cormorant colony on the way, and I think there is a sea lion colony at certain times of the year too. The boat trip took 4 hours, then we transferred to zodiacs after lunch to continue up the Rio Serrano to TDP, a 2 hour ride with views of Tyndall and Geikie glaciers. On sunny days a very good way to get to the park. We had rain, not heavy but enough to discourage looking at the scenery, and it was a very cold ride despite the thick jackets given to us. Wear thermals.
We hiked the W staying at refugios which were very well heated, most nights I slept only in a sleeping bag liner and definitely did not need a 4 season sleeping bag. No mice seen (the guidebooks suggest rodents can be problematic) but it was dusty, I woke up sneezing every night. Take ear plugs, even if there are no snorers in your room, some of the refugios have rooms where the walls don't go all the way up to the ceiling so you'll hear lots of noise. Refugio Pehoe (now called Refugio Paine Grande) is the newest and most comfortable, although a little impersonal. Refugio Grey is the least comfortable on the W, refugios Los Cuernos and Chileno the most scenic.
The Valle de Frances is worth the climb, wonderful wonderful scenery. Unfortunately we didn't have time to get past Campemento Britanico but I'm told it's spectacular at the end.
We woke up at 3.30am on the last day to get up to the towers for sunrise. Lots of people did the same so you can't really get lost, just follow the torches. It's REALLY cold waiting for the sun to come up so take lots of warm clothing.