You need to insert a group on item. If you don't want your main report organized that way, then insert a subreport that has an item group and then insert your crosstab in the subreport. Then create a formula {@null} by going to field explorer->formula->new, naming it {@null} and opening and closing the formula area without entering anything. Then create two additional formulas:
//{@summaryfield} to be added as the summary, with sum as the summary (not count):
if count({table.sales},{table.item}) > 50 then
1 else tonumber({@null})
//{@label} to be used as the row field:
if count({table.sales},{table.item}) > 50 then
{table.item} else {@null}
Then go to the customize style tab->check "suppress empty rows"->check "suppress empty columns".
-LB