I never won the thousands odds yet. The max odds I've ever won on sports betting is just two-digit odds. If you never tried this before because you think it's just wasting money, it probably is. However, I am sure after you read the story of that guy who won those thousands odds, some or most of you will try it too. IMO, the most important thing before you do that is setting a daily/weekly budget, how much you will spend (count it as a loss even before you place your bets), and sticking to that budget strictly.
You are absolutely right, I have a perfect simply experience as well with parley betting, infact, myself do more of parley betting than single bets even though I understand the risk involved in the two, single bets are easier to predict and win while parleys are harder to win.
I've been betting on parley with thousands of odds and for some, yes hundreds of odds or less and so on, but just like you the highest odd I've ever won on parley is two digits, and that was 58 odds and the ticket wasn't even a ticket I built myself, it was a ticket I copied from an unknown users on stakes betting log.
That is from time to time especially when I am very lazy for any research, I usually will open stake and scroll to the betting log in the sports betting section and there, you will see in real time betting tickets of all the players who choose to show their ticket in the log, one can click on any of the tickets, copy the games in the ticket and bet on it as well.
This was how I won that 58 odds parley with 8 different legs of matches, it was a super amazing experience and I hope that one day, I will surely win a parley with thousands of odds, if not actually hundreds of thousand odds.