It'll be in the "single.php" file.  You're looking for the variable name:

"$mkt_currency_symbol"

In Market 4.x it's around line #62:

&ndash; <span class="price"><strong><?php echo $mkt_currency_symbol; ?></strong><?php echo $price; ?></span>

Just change it to this;

&ndash; <span class="price"><?php echo $price; ?></span>

That'll take it out of the headline area, but not the dropdown boxes.  If you want it removed from those, then you'll have to remove the variable in the other places as well.

There's another one called "$CURRENCY_SYMBOL" as well.

To keep it from showing up on the page, you'll