Recently, I priced rough sawn timber, which is suitable for use in building raised beds. When building raised beds, it is often preferable to use un-treated timber as this will not leech chemicals into the soil used to grow vegetables. Timber lengths cost approximately fifteen euro for 4870mm length that is 225mm mide and 22mm thick. Thicker lengths of timber cost more. A 48700mm piece of timber will allow you to build a raisd bed that is 1200mm by 1200mm wide, giving 1.44 square meters of growing space. This bed would be 225mm high.
A four meter by two meter bed would require three lengths of timber, or 45 euro.
Other costs for building raised beds are fairly minimal, screws/bolts to secure the timber lengths together.
Topsoil and manure are often free if you collect it yourself.