Well a construction wooden beam is 68mmx38mm and kost about 1€ per meter
steel 50x50x3 kost about 3 to 4 euro a meter

so it will be a lot cheaper but jes then i would make it with haf lap joist and srew en glue everything together
everything thats steel will be bolted trough the wood .

and triangulation trusses in both way's?