Database size with large objects

I'm running postgresql 8.1.8 on RHEL4.

I have a database with a single table that includes an oid reference to a
large object.  After loading 100GB of large objects using lo_import(), I
find that my total database size has grown by about 270GB.  What is the
reason for the difference in space usage?

There are about 400,000 records in the table, with each large object the
same size (on average).  I have autovacuum running, and had done a vacuum
--full --analyze prior to the load.

Max_fsm_pages is very high (1,500,000), and the vacuum --analyze confirms
that it is sufficient.

Is this just something that I have to live with?

Thanks,

Mike