Cross-brand cannibalization: a $650K/month MCC case study

I discovered that my own campaigns were bidding against each other and I was losing money to myself.

Running Brady, Seton, and Emedco under one MCC creates massive auction overlap. All three brands bid on the same core keywords: "safety signs," "marking systems," "inventory labels." When a user searches "arc flash warning label," multiple brands show up. Google takes the highest bid. Sometimes that's Brady. Sometimes that's Seton. Doesn't matter to Google. They get paid either way.

But to me, it matters. Because I'm bidding my own brands up against each other, artificially inflating my CPC.

I found instances where Seton was bidding $8 and Brady was bidding $7.50 on the exact same keyword. Google showed Seton (higher bid). We won the click. But we paid $8 instead of $5 (the true market rate) because our own brand was competing.

Across the portfolio, this was costing me about $40-50K a month in wasted bid premium.

How to spot it

Pull your search term report for each brand. Look for exact duplicates across brands.

Do a domain analysis. Count how many clicks each brand gets on the exact same query.

Cross-reference with auction insights. If multiple brands are showing on the same keyword, check the bid levels.

What you're looking for: the same query triggering the same keywords across different brands, with overlapping bids.

When you find it, you've found money sitting on the table.

The fix

Three approaches, in order of complexity.

1. Keyword-level negative siloing (simple): Add all Brady keywords as negatives in Seton. Add all Seton keywords as negatives in Brady. This prevents direct overlap. A user searching "Brady marking system" will only see Brady. A user searching "generic marking system" might see either, but they won't both bid on identical terms.

2. Account-level bid capping (medium): Create rules that say "if this keyword is active in Account A and Account B, Cap the combined bid to X."

This is more complex because it requires script monitoring across accounts. But it prevents the bidding war.

3. Demand assignment (hard): Route demand to the brand with the highest margin or best conversion rate for that keyword.

If Brady converts at 15% and Seton converts at 8% on "arc flash labels," give the keywords to Brady. Remove them from Seton.

This requires historical analysis and ongoing monitoring. But it optimizes for actual performance, not just raw bid.

The real solution

I ended up doing a hybrid.

For high-overlap, high-value keywords, I use demand assignment. Brady owns "arc flash labels" because they convert better. Seton owns "chemical warning signs" because those convert better for them.

For lower-overlap, lower-value keywords, I use simple negative siloing.

And I monitor monthly with a script that checks for new overlap. When overlap appears, the script alerts me and I manually decide whether to silo or reassign.

The result: I eliminated the $40-50K/month cannibalization. Bids normalized. CPCs dropped back to market rate.

Why agencies miss this

Most agencies manage accounts in isolation. They don't have visibility into other accounts in the same MCC. So they can't see that they're cannibalizing.

If you're in-house managing multiple brands, this is something you can find in a week of analysis. If you're using an agency, ask them directly: "Are our brands bidding against each other? Show me the overlap."

If they can't answer that question quickly, they're not looking at the MCC holistically. Which means they're probably leaving money on the table.

The fix is straightforward. The win is real. And at scale ($650K/month), it's a six-figure decision.