How to figure value of a lofted sleeping area?

Lofts are hard to sell if priced as a one-bedroom and the lofted area is under 6'. If priced like an expensive studio then the loft is more likely to be viewed as a great "bonus" and the apartment would sell quickly. So, it all depends. Building comps will be very important here in determining value. You certainly seem to have identified comparable buildings in the GV area.
The 111 Fourth units with the soaring windows have a real 'wow' factor that just grabs people. If the price is right, those can be interesting units. But I personally do not care for windy litte stair cases to a hobbit-sized sleep area interupted by annoying columns making the space difficult to configure. The 67 E 11 St units I find to have awkward layouts for the most part and while the building exterior is quite attractive, I'm not enamored of the units themselves. On the other hand, many of the apartments are larger than 111 Fourth so on balance you get more space but no real 'wow' factor--its a tradeoff. 77 Bleeker is just plain ugly--reeeaaally ugly. I'd expect lower prices than the above 2 buildings. Plus if you are on the Broadway side of 77Blkr, the noise is a real issue you have to consider. Of the buildings you mention, 35 E 10th is my favorite location. I've lived near the NYU dorm on 5th Ave and 10th and didn't find it a problem although it can generate some noise in the area around it; by and large the kids are actually quite fun to have around. 39 E 12th St is also a prime location. Don't know the building though.

Instead of pricing the loft, I will add a premium for high ceilings. Say 8 ceiling foot post war trades at $1000 psf. 10 Foot will be ~10-15% premium. 12-13 at 20-25%. 16 or higher at a bigger premium as you can genuinely have two floors.

Well, here is an interesting comparison in the Cast Iron bldg. Unit 603 is a basic studio at around 425sq ft. Unit 503 has similar layout but has a sleep loft that is 5'8 and 12' ceilings. Are the high ceilings and sleep loft really worth $175k difference. The closet off the sleep loft is also not full size. Please help me understand this. Maintenance is only $40 more for the unit with the higher ceilings.

http://streeteasy.com/nyc/sale/597451-coop-67-east-11th-street-greenwich-village-new-york

http://streeteasy.com/nyc/sale/595111-coop-67-east-11th-street-greenwich-village-new-york

503 also has a balcony. 5th floor is the highest floor in 67 that has balconies, so there is also no balcony above you.

disregard my last post.. just looked at the floor plans again, and I see that the 6th floor DOES have a balconies. sorry..