What a great question, we've wondered the same thing as well. Our biggest temptation is to plant too many varieties in our limited area, leading to very close planting. If you keep yield records, perhaps comparing this year with next year can help shed some light on this ;) There are a lot of factors that may make this difficult, but this Univ of Missouri site has a comparison of some of that data:

http://extension.missouri.edu/p/G6370

Note the highest yield per acre is at 15 sq ft per plant in their study for determinate plants. We use 5 sq ft per plant for mostly indeterminate plants, but a number of websites talk about 6-10 sq ft per plant as typical. At 350 pounds in a 150 sq ft area (100,000 lb per acre), our yield per sq ft is almost twice the U of M data. Similar to high density square-foot gardening.

Please let us know how it turns out.

I've personally seen more production in the tomatoes I let sprawl as large as they'd like, pruning only to remove diseased leaves and keep them off the ground. The upside for me in crowding them (even though I still try to keep 3' between plants because I'm not a big pruner) is that I can try more varieties in my very small garden.

I'd also be interested in how it turns out if you do any comparisons.

"We use 5 sq ft per plant"

That sounds pretty good for a commercial operation.

The highest production they (UMO) listed is for cage ( 2 1/2 by 6 ).

The 6 foot is just walkway between the rows for service and harvest.

So in effect the plant uses a 2 1/2 by 2 1/2 square area. That is ~ 6 sq-ft per plant. But that is commercial operation. We, the backyard gardeners in a small lot / raised bed can do much better than that. I don't need a walkway in a 3ft x 6ft bed. I can be very generous to plant 4 to 5 in it but I plant 6 ( I am cheap :-)

Most tomato spacing recommendations call for 2 to 3 ft spacing. So if I was going to plant in rows, I would space the rows 3 ft apart and the plants in the rows by 2 ft. That is 6 sq-ft per plant. Any spacing beyond that is inefficient use of land and resource. JMO

Sey