Hello
The absolute number of Steem increases, the value per Steem Token is constant or increases, the total value of my account increases and that is a net gain.

Example;
I start the year off with 100 tokens, worth 0.25 USD each
Total account value $25.00 USD

Annual inflation of 8.5%
Tokens awarded my account 8.5
NEW TOTAL TOKENS 108.5
NEW ACCOUNT VALUE $27.125
ROI = net profit / total investment
ROI 2.125/25
ROI= 8.5%

Add curation of 8.5%
Now token gain doubled 17 tokens
Net profit = $ 4.25
ROI = 4.25/25
ROI= 16%

This doesn’t include any author rewards I earn only fixed token inflation and conservative curation earnings, so my ROI will be greater if I post.