DUO curation is one of the attractive features of staking DUO. I realize that this only one feature of DUO and that the upvote will increase in value as HP grows, but here's some math for context where the DUO curation rewards stand right now, the current 70% curation will earn the investor about 32% if they are curated daily.

200 DUO x 0.5 HIVE = 100 HIVE
HP 6326, VP 80%, Weight 70% = $0.0391 x 50 % author reward = $0.01955 / $0.22 = 0.0888 HIVE reward X 365 daily posting = 32.412 HIVE = 32.412% APR (Just Daily Curation Rewards)

Source

For Tiered Curation, the investor will earn 9% - 6.5% depending on the tier.

200 DUO x 0.5 HIVE = 100 HIVE
HP 6326, VP 80%, Weight 20% = $0.0112 x 50 % author reward = $0.0056 / $0.22 = 0.0254 HIVE reward X 365 daily posting = 9.29 HIVE = 9.29% APR (Just Daily Curation Rewards)

500 DUO x 0.5 HIVE = 250 HIVE
HP 6326, VP 80%, Weight 40% = $0.0223 x 50 % author reward = $0.0111 / $0.22 = 0.0507 HIVE reward X 365 daily posting = 18.49 HIVE = 7.4% APR (Just Daily Curation Rewards)

1000 DUO x 0.5 HIVE = 500 HIVE
HP 6326, VP 80%, Weight 70% = $0.0391 x 50 % author reward = $0.01955 / $0.22 = 0.0888 HIVE reward X 365 daily posting = 32.412 HIVE = 6.48% APR (Just Daily Curation Rewards)

Of course these APR will half for new DUO stakers who purchase at 1 HIVE. Investors gain other benefits as they increase their stake, but the curation APR for curation will become less efficient as they grow their stake.