IF Calculation: Calculating Costs Of Products Ordered Which Imports Quantity And Descriptions From Another Sheet

I have a form for calculating costs of products ordered which imports quantity and descriptions from another sheet. The imported info and basic calculation of appropriate cost based on ordered quantity seems to work okay. These formulas are as follows:

First column: =IF(ORDER!A5>0, ORDER!A5, "") inserts the quantity ordered
Second Column: =IF(ORDER!A5>0, "Part Description and Part Number", "") inserts the product description

Both those formulas return a blank cell if nothing is ordered. Then using an outlying cell (G3) I enter the following formula to determine appropriate cost based on total order quantity e.g. $2.57ea if total ordered quantity is less than 50 and $2.37 if total quantity is greater than 50.. {Q: How do I put a third pricing level in here??}

=IF(SUM(A5:A27)>50,"$2.57","$2.37")................