any idea on cost to repair crankshaft seal on 1993 Honda Accord LX?

I would say on the high end 450$. There could be some leeway in the price based on a visual inspection.

When Dale45 says $450, that would includes replacement of the timing belt, water pump, idler and tensioner pulleys and both crank and cam seals.

Front or rear crank seal? Above answers are correct unless it is the rear crankseal which would involve transmission removal. Parts and labor approx $550.