How would I structure a formula for the following problem:

The wages for YoYo Joes will increase if the number of items sold each month exceed 25500. The calculation 
of wages includes a fixed base amount of $175000 plus an increase of Excess_Production_Cost per 1000 
units over (rounded to the nearest 1000). In order to calculate this amount, both the IF function and Round 
function must be used. If the number of units (widget units and gadget units) exceed 25000, then the wages 
are equal to the number of units over 25,000 rounded to the nearest 1000 (precision is -3) times the 
Excess_Production_Cost assumption plus $175000 otherwise it is just the $175000.

Try this:

=IF(NoUnitSold>25000, 175000+ROUND(NoUnitsSold-25000, -3), 175000)