For whatever reasons, maybe because I've gotten better, maybe luck, but anyhow, I found it harder to get a very high win-rate at the $10 level than I have at the $20.
Be that as it may, I'm still playing HU largely for fun--obviously with the intention of winning, but I don't see the income level as very high unless you're going for higher buy-ins.
Let's just say that you can make 70% at the $10 level. Then after 10 matches, you've won $140 gross, and you've put in $110, so you've actually made only $30 net. That's really not a very high hourly rate.
The effective rake does decline if you do the 4-player tournament style. But, again, let's say you have 70% both at first table and at last table (the player in the "final" is definitely likely to be stronger, so that's probably rather optimistic for the second game).
Your probability of winning the tournament is then exactly 49%, so let's call it 50% just to make it easy.
Again, you play 10 tournaments and put in $110. Now you win $200, since the prize pool is better. Well, that's $90, but you've also played significantly longer. Still, it is getting into the range of an actual hourly wage. But you've also put in twice as much time on the ones that you do win, and also a lot of time on the ones where you make final table and lose.
Anyhow, I'm not completely convinced that the 2-table HU matches are really much better than the 1-table ones--largely because I have trouble attaching an actual percentage to win-rate at final table. It objectively does have to be lower than your overall win-rate.
For me, anyway, I guess if I can keep the 70% up at the $20 level, that should mean that I'm netting $60 over 10 tournaments, which probably average something like 30 minutes each (sometimes it's over in 3 hands, sometimes it turns into one of these long drawn-out battles, but 30 minutes sounds like a reasonable average). I guess, really, $60 for 5 hours of play isn't bad. It's more than $10 an hour, and that's not entirely easy to do in a $100 cash game (if you play 60 hands an hour in a cash game, you'd have to be averaging something like 18 BB/100 to match that, and that's a pretty decent win rate, I think).
But I'm still a bit skeptical about keeping up the 70%...

While I did feel like I was constantly getting sucked out when I was down a little below 60%, 70% feels pretty strong to me, although maybe it's sustainable or even beatable...