If the chips are valuable sell them separately
If they are worthless sell them as a set

If they are neither of the above then...

It depends what price you are willing to start them at. If you started them at 99c you are likely to get more selling separately and make a reference in the description to the others being on ebay also. If you start them at a higher price you run the risk of not selling all 4 and perhaps getting less than if you kept them together.