if it`s of any use to you for Future ref, I`v found that 3 pounds of tomatoes when cooked down and sieved of the skins and pips, then reduced down to Pizza sauce consistency (to my Own liking), is enough to do 2x 15" pizza bases.
I`m not sure how this compares with shop bought toms though as mine are homegrown as a rule.
V8 reductions are Very nice too, I use that for thick soups ;)
also be very careful when you add salt! you can "hide" Massive amounts of salt in Tom sauces and hardly even notice it`s there, I`m not sure How it works, but don`t go by Taste for salting, if you Can taste it, there is probably a Dangerous amount in there.
Sugar is similar too with Tomatoes.
So long and Thanks for all the Fish ;)