Don't know the cost, but a "sender" for an oil pressure guage is either just a tube moving the pressurized oil to an internal Burtonoli? tube/mechanical linkage inside the guage that moves in relation to the pressure....
Or it is a "true" electrical sender, basically a variable resistor/rheostat to ground, as both have been used on HD's as standard and aftermarket equipment. I would check your service manual or electrical schematic if true std HD guage or identify vendor of guage (check for stampings or model #) to determine which type you have.