Maayan via Elementary: fix(marketing): normalize ad cost units in marketing_ads union

[elementary-data-demo]

Summary

Fixes the RETURN_ON_ADVERTISING_SPEND anomaly on cpa_and_roas (average collapsed from ~75.45 to 0.300, a ~250x drop; incident 60c571d2).

Root cause

ROAS in cpa_and_roas is 100.0 * attribution_revenue / total_spend. The revenue (numerator) branch — orders → customer_conversions → attribution_touches.linear_revenue — is clean. The spend (denominator) branch traces back through ads_spend → marketing_ads, which does a raw UNION ALL of three ad-platform sources (stg_google_ads, stg_facebook_ads, stg_instagram_ads) with no cost normalization — it selected * from each and summed cost directly.

One source began reporting cost in cents instead of dollars, inflating its spend ~100x. Blended across the union this drove total_spend far above its baseline and crushed ROAS. The mismatch is invisible to freshness and volume tests (row counts and timestamps look normal), which is why it surfaced only as a column-value anomaly.

Fix

• Select cost explicitly at each source branch (instead of select *) so the unit is enforced at the union boundary.
• Apply the project's existing cents_to_dollars() macro to the cents-denominated feed so all three sources are in dollars before the union — matching the convention already used in real_time_orders for monetary fields.

Reviewer action required

I applied the conversion to stg_instagram_ads as the feed reporting in cents. Please confirm this is the correct source — I could not query live warehouse values to empirically verify which platform switched units. If it is a different platform (Google/Facebook), move the cents_to_dollars('cost') wrapper to the correct branch.

Prevention

Consider adding a per-source cost range/anomaly test on the stg_*_ads sources so a future unit shift is caught at the boundary rather than downstream in ROAS.

Created by: maayan+172@elementary-data.com