Well, talking about the Inlandsbanan and "Budget" do not fit in one box IMHO.
A one-way Östersund-Gällivare sets you back 1378,-SEK (ca. 675,-Lei) unless you travel on an Interrail ticket. In that case you only pay a surcharge of 50,-SEK (ca.25,-Lei).
See also the Inlandsbanan website: inlandsbanan.se