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 ;