Marmot Eco Pro 30 Sleeping Bag: 30 Degree Synthetic - 2008 BCS

According to the specs Marmot has on their website this bag is 2lbs 14oz. I'd go with what Marmot says since every once in a while Backcountry does mess up and get information wrong. Also I've seen it where the weight posted is for bags without the stuff sack. I'm not sure that the stuff sack on this would weigh 13ozs but it could also be a reason for the differing of numbers. Still, I'd probably just believe Marmot's numbers in this case.

As long as they are the same length then yes they will match up fine.

It really depends upon your preferences, and your size. If you like being snug in your bag (or are very interested in saving weight) a regular would likely be OK. If you may be pushing the bag to its temperature rating or beyond, a snugger bag may help keep you warmer. But if you want a little more wiggle room then get a long. The long is not only longer, but also a little wider, so if you are a stocky 5'10 then a long might be more comfortable. Personally, I prefer my bags a little on the longer side, because for me the extra wiggle room is more important than the slightly increased weight.

Another thing to keep in mind is that, generally speaking, 15-30 degree bags are traditionally 3-season bags. Meaning they're good for spring/summer/fall. However, if you're in southern/central CA (not sure about northern)it should be good for the winter too. Use a pad and put on clothes if you get cold.

To answer the first part of your question, I dont believe the "eco-friendliness" has much to do with the price of the bag. However if you notice, there are two prices listed above. Thats because there are two different size bags and simply put; more material = more money. As far as pricing factors, there are all sorts of things that contribute to the price. Material's used, filling (Down bags cost a ton!), temp rating, size, weight, compression sacks and other goodies, whether its this years model or last years, how many the company still has in stock, the list goes on.
I bought this bag a few weeks ago and Ive slept in it twice. If you're looking for a solid, fairly light bag that'll keep you warm for everything but winter camping, then you should seriously consider this bag.
Hope this helps!