With only letters "hippo.com" has value, although still a very low buyer pool as the use cases are incredibly rare, so maybe not as valuable as one might think.
Your versions have the same incredibly rare use case for a domain solely about "hippo", but additionally yours replace letters with numbers, and unless premium or interesting in some way, such domains just don't ever sell.
Business don't want to have to explain how their business domain/website works, in that the "i" is a "1" and the "o" is a "0". For business this is very bad, eg on the phone "no it's h one pp zero". And they'd be better with a good branded name or two word combo "HippoSomething".
".io" are rare to sell, even with premium words. Yours simply wont ever sell.
The ".com" is reg fee I'm afraid. I genuinely just don't think it'd sell even with all the visibility and years you could give it.
You should spend a lot of time reading the market place forums and sites like namebio.com to see what sells. And remember that the sales reports only show what sells, not the tens of millions of domains that never sell
Good luck