The only thing you'll save is estate agents fees. You'll still have legals and you'll still have stamp duty. It was something useful years ago when you only paid stamp duty on the difference in value between the two. Not anymore. Stamp duty is applicable on each of the values of both of the properties.
A long time ago this method was used for county council tenants who wanted to move to another area. For exam if you'd been allocated a house in Finglas but you wanted to live in Clondalkin, you'd swap county council houses.