How To: A large [2D] matrix, 100,000+ rows/columns

Experts,

A very high level question... Subject sums it up.

I love PGSQL, but I don't know if it is a good fit for this back-end... I
hope it is.

Imagine something akin to stocks, where you have a row for every stock, and
a column for every stock. Except where the same stock is the row & col, a
number is at each X-Y (row/column), and that is the big picture. I need to
have a very large matrix to maintain & query, and if not (1,600 column
limit), then how could such data be broken down to work?

By wanting postgresql as a solution, am I round-hole, square-pegging myself?

I don't mind keeping, say, a 1,500 column max per table, but then adding
new items (stocks in the above analogy) might make it difficult to keep
track of things...

Hoping someone has tackled this before, and performance isn't too big a
concern, as the data changes seldom.

I know it's a weird one, so thanks!

:-)