From the "price" column, use the "Edit column" -> "Add column based on this column" option. If the value in the "price" column is already stored as a number, you can use GREL:
if(value>90,1,0)
otherwise you will need to convert the "price" value to a number in the GREL:
if(value.toNumber()>90,1,0)
You are using 1 and 0 here, but because OpenRefine supports boolean values I might suggest using true/false instead
if(value>90,true,false)
Best wishes
Owen