FYI:
$500 in 1930 after inflation is $4214 in 1992 according to the CPI, so there is no reason why Rav Yeruchum could not have had this laying around and/or sell some of his possesions to obtain the cash. 500 dollars in 1920 or 1930 would get you (therebouts of) $6750 today if we are dealing with silver dollars.