You can use a parameter to determine if sales at a record level are less than n.
If you have more than one record for each salesperson, you can do this a little differently with an LOD.
9.2 workbook attached.
This is so weird - it works like a charm, but I don't think I understand the logic behind this...
[Sales] is the value at each record level.
The formula applies to each record,
so Ben, $45,002 < $50k
Carey, $45,001 <$50k
All of these would return true. However, if you have more than one record per salesperson (which I suspect is the case), you will need Pooja's formula to calculate the SUM([Sales]) for each person. That formula calculates the aggregate and it becomes a row level value.
Here is a good blog on LODs if you want to learn more.