Trading currency basics

Tod = Tour of Duty (TF2 Item)
Ref = Refined Metal (TF2 Item)
TF2 = Team Fortress 2 (just in case XD )

They can be bought from the market or in-game
TOD is tour of duty ticket and ref is refined metal
Not sure of the conversion as it fluctuates
This might provide some info

11. How did you pay for your McDonnell Douglas product?
    _Cash
    _Suitcases of cocaine
    _Oil revenues
    _Deficit spending
    _Personal check
    _Credit card
    _Ransom money
    _Traveler's check
    source: http://www.cartalk.com/content/mcdonnell-douglas-warranty-card

Thanks IDrake and Akash.