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Around the middle of November, I decided to start crossposting 300+ items to Mercari and FBMP from Posh and eBay, primarily all stale inventory. In the later half of the month, sales of those items on Mercari and FBMP ended up accounting for 23% of my sales (# and $) for the month of November. I decided I would conduct a more formal experiment to see how sales look for a variety of categories across all platforms, gaining some insight and best data I can, considering this anecdotally based industry we’re in. 

Also somewhat inspired by this YouTube video, which was shared to me during this time: “200 Items Listed at the Same Price on eBay, Poshmark, and Facebook Marketplace – What Happened?”

Outline of the experiment, thanks to the scientist within:


  • See what items do best/better on eBay, Poshmark, Mercari and FBMP, while listing at same price on all platforms, and measuring sell-through, ASP, offers vs full price, and average fees (I’m a data nerd so I suspect there will be more). 
  • I don’t have a quantity or time frame in mind, that will evolve as this needs to be maintainable so that I’m still making the sales I need for sake of bills, but also so I don’t get overwhelmed and behind on tracking, or forgetting to keep LP updated as they sell. 
  • Daily updates, mostly just notes and light summary. I’m not intending everything I list, everyday, to be part of this. 
  • Weekly, some more thorough data with numbers!


  • Work through ‘death pile’, but also add new inventory as it comes in. 
  • List on eBay, import into LP, then cross to Mercari, Posh and FBMP, and in the same day, preferably back to back.
  • Pricing the same, and competitively to leave some wiggle for offers but also very reasonable and ideally likely they purchase as listed.
  • No offers sent immediately, but I will entertain about 20% off, and all this will evolve with time.
  • No sharing on Posh. Fired my assistant. 
  • eBay will auto renew every 30 days, FBMP weekly renew/auto delete re-list as it comes up. Undecided at the moment on Posh/Mercari re-listing.
  • Shipping will be standard/cheapest practical on each site. Will include Local Pick-up on Mercari and FBMP just because. 


  • Very few items will have ever been listed. A few right off the bat may have been on one site at one point, but were old, crappy listings and ultimately entirely redone.
  • Initial inventory is ‘new to me again’ pile, some of which is death pile, some has been bought in bulk and intended for rainy day.
  • It will be quite an eclectic mix and I never would have intended most to be on some sites, but that’s usually when you’re pleasantly surprised. 
  • The rest will be new inventory as I start sourcing again. 
  • I do have eBay only collectible type items that I will be listing there as well, but not elsewhere and those will be excluded from the ‘experiment inventory’.
  • I anticipate still picking up items that won’t be part of this for any number of reasons – such as brands (ones notorious for issues on FBMP), sell through rate, not suitable for universal pricing or prohibitive due to nature of item and shipping costs/weights. 


  • No sharing on Posh – if coupled with lower sales there and more on other platforms, I suspect that may indicate sharing does have an impact and is essential to make sales as most believe. However, also that sharing is total BS and a waste of time because I clearly have desirable items that can be sold elsewhere with less time and effort involved.
  • No immediate offers on Posh, as tends to be the culture and expected – both that sellers need to do and buyers wait to buy. Similar to sharing, could be somewhat telling of whether OTLs (offers to likers) makes a difference. 
  • I suspect eBay will still be the front runner, perhaps Mercari second, and toss up between FBMP and Posh. Partially due to FBMP having (I suspect) still lower traffic, and Posh due to sharing/offers.
  • I’d hope FBMP could pick up given their 5% fee versus the 12-15% on eBay and Mercari, and then 20% on Posh, coupled with fact it’s less time intensive.
  • I’m not sure what will do best where, but that is the beauty of this and part of the purpose to gain that insight. 


Day 1: November 29, 2021

  • Listed 21 mens, 1 woman’s button up shirts (mostly cowboy, some Hawaiian)
  • $21.67 avg list price, $3.99 avg COG
  • *one shirt (vintage Dior Monsieur) rejected by FBMP, but I did leave up on the other 3 

Day 2: November 30, 2021

  • (6) Vintage women’s vests (mostly denim jean style) 
  • (10) Kate Spade items, mix of some that had been up on one. Got them up on eBay and LP, then had to step away, and one sold before could get up on others. Then had one sell immediately on Posh for full price. 
  • (18) Victoria’s Secret/PINK, another one with some listed before, but also very limited and to one platform. 
  • $23.68 avg list, $1.70 avg COG (*note: half of these items are my personal ones I need to purge so I’m throwing in $1/COG each for those).

Total Listed


Total Sold


Total Offers