Hi @cp_sk
As you’ve found, HubSpot campaigns at present don’t have comprehensive cost tracking features built in and therefore don’t nativley allow you to report on true ROI.
There is an idea suggesting it here: https://community.hubspot.com/t5/HubSpot-Ideas/Recording-campaign-costs-to-calculate-ROI-for-campaigns/idi-p/342976 and I see references to Salesforce offering more in this area. Therefore it could be a good Enterprise feature for HubSpot to consider in the future.
Its probably a fairly tricky problem to solves as spends don’t necessarily split down neatly into campaigns, but it would be an interesting addition to HubSpot.
Hope this helps.