How much bigger does a precomputed lookup table get when salt is added? I am trying to wrap my head around the benefits of salt in cryptography.

http://en.wikipedia.org/wiki/Salt_(cryptography)

I understand that adding salt makes it harder to precompute a table. But exactly how much harder do things get with salt?

It seems to me, like when you add salt, the number of entries in your precomputed table would = number of common passwords to precompute x number of entries in the password table (ie number of different possibile salts).

So if you have a list of 100 common passwords, then without salt, you would have 100 hashed passwords. But if you have 10 users on a system, with 10 different salts, then you would now have 1000 different combinations to check.

So as the numbers of users or the size of common password list increases, the precomputed table gets so big that you can't pre-compute it easily (if at all)

Am I getting this? Do I have it right?

NoteCross posted on cs theory https://cstheory.stackexchange.com/questions/11118/how-much-bigger-does-a-precomputed-lookup-table-get-when-salt-is-added#comment30381_11118 CS Theory Users suggested I post here too
Looks right to me, assuming you know what the 10 salts are. 

If you don't know a priori what the salts are (which is typically the case when building a rainbow table), you'd have to compute for the entire salt space. This is where the big gain comes into play as for each additional salt bit, the storage requirement doubles. Thus you get exponential growth of the storage requirement.