Exhibit 10.4

PROMISSORY NOTE

March 15, 2006

$4,160,000.00

FOR VALUE RECEIVED, the undersigned, HyperFeed Technologies, Inc., a Delaware
corporation (“Borrower”), promises to pay to the order of PICO Holdings, Inc., a
California corporation (“Lender”), the principal sum of Four Million One Hundred
Sixty Thousand dollars and no cents ($4,160,000.00), together with the interest
thereon at the rate of seven percent (7%) per annum, commencing on the date
hereof and continuing until the principal sum is paid in full. Interest shall be
computed on the basis of a 365-day year.

The parties acknowledge that Borrower borrowed the principal sum of $3,310,000
from Lender in a Promissory Note dated February 15, 2006.

The parties agree that an additional principal sum of $850,000 shall be borrowed
from Lender in this Promissory Note dated March 15, 2006 and that the principal
sum borrowed by Borrower from Lender in the February 15, 2006 Promissory Note
and this March 15, 2006 Promissory Note totals $4,160,000. The parties also
agree that the February 15, 2006 Promissory Note totaling $3,310,000 is hereby
cancelled.

The entire unpaid principal balance of, and all interest under, this Promissory
Note shall be due and payable not later than April 30, 2006. The indebtness
evidenced hereby may be prepaid in whole or part at any time without penalty.
Any payment or prepayment shall be applied first to interest and second to the
principal due and payable hereunder.

HyperFeed Technologies, Inc. covenants that, if suit be brought to enforce the
payment of the principal or interest under this Promissory Note, it will pay
PICO Holdings, Inc. such further amount as shall be reasonable to cover the cost
and expense of collection including reasonable attorney fees.

HYPERFEED TECHNOLOGIES, INC.

/s/ Gemma Lahera          
By: Gemma R. Lahera
Title: Principal Accounting Officer & Treasurer