I don't know where all these guys are getting THEIR numbers from, but here's what I'd say just based on reading up on AFs over the last couple of months:
150 should be NO problem evenly-spaced in a 30x30 area. If you placed them each a foot apart, you'd have 30 rows of 30 plants (or 900 plants total). You only have 150 plants. If they're spaced evenly, there should be about 12 rows by 12 rows (or 144 plants) with each plant spaced about 2.5 feet from the next. Absolutely NO PROBLEM for most autos.
You can expect up to an ounce from each auto, depending on it's strain and pheno of course. If you're doing easyryder or dieselryder, you could expect these numbers to be higher, but like D mentioned in the above post, you can expect 1/4 to 1/2 oz off each LR2 outdoors (I've read the autos typically do better indoors at 18/6 the whole time).
If we go with an estimate of maybe a half to 3/4 oz off each (5/8 of a ounce off each plant), times 150 plants, equals about 94 ounces, or about six pounds. D said in the previous post that he gets 8 to 12 grams per plant. That's about half this. So if it's LR2 you're growing, you can expect more like 2-3 pounds.
This is, of course, assuming these plants are all female. If not, I'd cut those numbers in half again just to be safe.
To those who think autoflowers are a waste of time. These 150 plants could be planted within eyesight of a major highway without being seen. And when MJ does become legal, not everyone will bother growing gigantic plants. The autoflowers will become even more popular, as people will be able to plant them around their yard without making a BIG thing out of it. It's not like those humongous plants are gonna be worth anything anyway. Nobody's gonna pay out big money for something they can grow out in 60 days in their own backyard.