Amazon Ads: the most mature and most competitive
The largest and most sophisticated marketplace ad platform, with the widest range of formats (Sponsored Products, Brands, Display, and more, plus DSP for larger advertisers) and the deepest measurement tools. Also generally the most competitive and highest-CPC environment for popular categories, simply because of Amazon's traffic volume and advertiser density. Its search term reporting and targeting options are also generally the most granular of any marketplace, which makes it the platform most sellers should learn advertising fundamentals on, even if they plan to advertise elsewhere too.
Walmart Connect: similar mechanics, generally lower competition
Structurally comparable to Amazon Ads (see How to Set Up Your First Walmart Connect Campaign), with generally lower CPCs due to lower overall advertiser competition — often a comparatively efficient place to advertise for sellers already established there, though absolute traffic and sales ceiling are lower than Amazon's. Expect a longer ramp-up to gather meaningful data given the smaller search volume.
TikTok Shop Ads: newer, discovery-driven, and creative-dependent
Distinct from the other three in that performance depends heavily on video creative quality and format-native content style, not just targeting and bid — a poorly-produced ad underperforms regardless of targeting precision. Well suited to impulse-driven, visually demonstrable products; less suited to considered-purchase categories with long research cycles. Sellers coming from a purely search-driven advertising mindset (Amazon, Walmart) often underestimate how much of TikTok Shop Ads' performance depends on the creative itself rather than the targeting settings around it.
eBay Promoted Listings: simpler, cost-per-sale model for its main format
eBay's primary Promoted Listings Standard format charges a percentage-of-sale ad fee only when the promoted listing actually sells (rather than cost-per-click), which removes the risk of paying for clicks that don't convert but also means the mechanics and optimization levers differ meaningfully from CPC-based platforms — there's no bid-per-click to tune, no search term report to mine in the same way, and the main lever is the ad rate percentage itself.
Side-by-side comparison
| Amazon Ads | Walmart Connect | TikTok Shop Ads | eBay Promoted Listings | |
|---|---|---|---|---|
| Cost model | CPC (+ DSP programmatic) | CPC | CPC / CPM (varies by format) | Percentage-of-sale (Standard format) |
| Relative competition | Highest | Lower than Amazon | Format/category dependent | Lower, simpler auction |
| Key success driver | Bid + relevance + conversion history | Same mechanics, less data volume | Video creative quality | Ad rate percentage set |
| Reporting depth | Deepest, most granular | Comparable structure, smaller data volume | Growing, less mature than Amazon | Simpler, less granular |
| Good first platform to learn on | Yes | After Amazon fundamentals | Only if selling visually strong, impulse-friendly products | Simple to start, less to optimize |
A practical allocation approach
Most multichannel sellers advertise most heavily on the marketplace(s) where they already have the strongest organic sales velocity and reviews — advertising rarely single-handedly overcomes a weak underlying listing, so budget follows proven product-market fit per channel rather than being spread evenly across all of them by default.
Worked example: allocating a multichannel ad budget
A seller doing meaningful volume on both Amazon and Walmart, with an emerging TikTok Shop presence, has a combined $2,000/month advertising budget. Rather than splitting evenly three ways, they allocate roughly in proportion to where organic sales and margin are strongest: $1,200 to Amazon (their highest-volume, most-proven channel), $500 to Walmart Connect (smaller but consistently profitable), and $300 to TikTok Shop Ads (treated as a smaller, higher-risk exploratory budget while they learn what creative style performs, rather than assuming it will match Amazon's efficiency immediately).
Mistakes to avoid
- Splitting ad budget evenly across marketplaces regardless of where organic sales and margin are actually strongest.
- Applying Amazon-style CPC optimization instincts directly to eBay's percentage-of-sale model, where the levers are different.
- Launching TikTok Shop Ads with repurposed static product photos rather than native-feeling video content, then concluding the platform "doesn't work" for the product.
- Judging a new platform's early results against an established platform's mature benchmarks within the first few weeks.
Best practices
- Let organic sales performance per marketplace guide initial budget allocation, then adjust based on each channel's actual ACOS/ROAS once you have data.
- Treat a newer or smaller-traffic platform's early campaigns as a longer-timeline learning investment, not a fast-fail test against Amazon-scale expectations.
- Revisit allocation quarterly as channel mix shifts, rather than setting it once and leaving it static.
FAQs
Should I advertise on every marketplace I sell on? Not necessarily from day one — it's usually more efficient to prove out advertising on your strongest channel first, then expand to others once you understand your own product's ad economics.
Which platform has the best ROAS? There's no universal answer — it depends heavily on category, competition, and how well-suited your product and content are to each platform's format (especially for TikTok Shop's creative-dependent model).
Is eBay Promoted Listings worth using if I'm used to CPC platforms? Often yes, precisely because it removes the risk of paying for non-converting clicks — but understand that its main lever (the ad rate percentage) works differently from bid-based optimization on the other platforms.