Should you advertise on Amazon and Google at once
Compare marketplace and search advertising on net contribution after fees rather than on return figures that are measured in different units.
Two channels asking for the same budget
You sell on Amazon and you sell on your own site. Both platforms offer advertising and both report encouraging returns and the budget that funds them is one budget. So the question arrives as a comparison and the comparison is made on the wrong number.
The two are not substitutes. Amazon advertising harvests people already shopping with a card out. Google reaches people researching a category and people looking for you by name and people who have not reached a marketplace yet. Running both is often correct. Funding them from a single return figure is not.
What each channel excludes
Amazon advertising excludes the customer. You do not receive the buyer's contact details and you cannot retarget them and you cannot email them next season. You are renting access to a relationship Amazon owns. It also excludes brand building since a shopper comparing on a results page is not forming an impression of you.
Amazon revenue also carries costs Google revenue does not. A referral fee and fulfilment and storage and returns handling come out before your margin and ad spend sits on top of that stack. A rupee of marketplace revenue is worth less than a rupee of own site revenue and every comparison starts there.
Google advertising excludes the easy conversion. A marketplace listing converts because the buyer already trusts the checkout. Traffic to your own site meets your own payment flow and your own trust problem. Service fees raised in India attract GST at 18% on top of the fee and a scoped marketplace optimisation engagement publishes what listing work is covered so you can see what sits inside and what does not.
Who should not run both
Do not advertise on Amazon while your listing is unfinished. Thin images and no A plus content and almost no reviews mean the ad buys a click onto a page that cannot convert. Fix the listing first. Anything else is paying Amazon to demonstrate your weakest asset.
Do not run both if your operations cannot hold stock. A stock-out during an ad campaign costs the campaign and the organic rank it was building. Single SKU sellers on thin margin should pick one channel and learn it properly rather than splitting a small budget twice.
And do not run Google ads pointing at your Amazon listing if you can avoid it. You pay Google for the click and Amazon for the referral fee on the sale and you lose the visitor data in between. It is the most expensive route to a customer available to you. Businesses with no website of their own are better served putting that money into marketplace advertising until a site exists.
How to divide the work
Give each channel the job it is good at. On Amazon run sponsored products against the terms your listing already converts on and expand outwards from there. Let exact match campaigns on proven terms carry most of the budget and keep a small automatic campaign running to discover new ones.
On Google take the demand Amazon cannot see. Category and problem searches where the shopper has not chosen a retailer. Your own brand name which protects you from resellers bidding on it. And traffic to your own site where you keep the margin the referral fee would have taken.
Keep pricing consistent across both. A lower price on your own site invites buyers to compare and a lower price on Amazon trains them to go there instead. Then watch total advertising cost of sale on Amazon rather than campaign level return since marketplace advertising lifts organic rank and the organic sales belong in the calculation.
The number to judge on
Net contribution per channel after all platform costs. Compare those two figures and nothing else. Marketplace sales need fees deducted first. Own site sales need gateway charges and shipping deducted.
The metrics that flatter are Amazon's advertising cost of sale and Google's last click revenue. Each is calculated inside its own platform on its own revenue definition and the two cannot be set beside one another. A healthy looking cost of sale on Amazon can still be a loss once fees come out.
The common mistake
The expensive error is moving budget between the two on platform reported returns. Amazon reports a strong number because it is advertising to people in a buying state. Budget shifts there. Nobody adjusts for the referral and fulfilment fees that Google revenue never carried. The business grows its marketplace share while gross margin falls and the two facts are not connected in anyone's report for several quarters.
The second error is letting Amazon become the only channel because it is the easiest. Dependence on one marketplace means your pricing and your visibility and your access to your own customers sit with somebody else.
A sensible sequence
Get the listing genuinely good. Then advertise on Amazon where intent is highest and feedback is fastest. Then fund Google once your own site converts well enough to keep the margin that justifies it. Running both at once is the right end state for most sellers. Starting both at once with a small budget and an unfinished listing is how the money disappears.
This guide explains how something works. It is not legal, tax or financial advice, and rules change. Confirm anything regulatory with a qualified professional before you act on it.