Unless I completely destroy the question in my head this is what you meant by two rows out of each one:

    create table #TableOne (
    	TxnId int, 
    	FromUserId int, 
    	ToUserId int, 
    	Price decimal(5,2))
    
    insert into #TableOne values 
    	(1, 1, 2, 100.01),
    	(2, 1, 2, 100.01),
    	(3, 2, 1, 100.01),
    	(4, 2, 1, 100.01),
    	(5, 3, 4, 100.01),
    	(6, 4, 3, 100.01),
    	(7, 4, 3, 100.01)
    
    select 
    	FromUserId AS FocalUserId,
    	TxnId,
    	FromUserId,
    	ToUserId,
    	Price
    from #TableOne 
    union all 
    select 
    	ToUserId AS FocalUserId,
    	TxnId,
    	FromUserId,
    	ToUserId,
    	Price
    from #TableOne