This is what a LOT of Asian sellers are doing at the moment with 3rd party logistics.
I know someone who does millions a year in sales on eBay alone and he uses a company called ES3. I've been looking into this for the past 6 months in the U.S. and U.K. and am about to set up a 3rd party distribution myself as I recently got to a level of sales where I think it's appropriate, I used to use 4PX in Hong Kong when I first started but made a deal with a business owner that had extra warehouse space in Shenzhen.
Heres some advice:
A lot of companies out there operate solely on the uneducated business owner and will squeeze, nickel and dime you with tiny little fees until you have 0 profit. This is kind of what Amazons Fullfillment does, it nickels and dimes you where they make a higher profit from warehousing your items rather than them buying those same items and selling them.
Do flat rates, even if it isn't always in your favor. For example:
0.06 labor cost per package
0.25 material cost per package
2.00 per box
1.00 a month per item per month of storage
is relatively flat rate. With these rates, I know my profit has to be higher than $3.31 so I can afford the have the item warehoused and sent out, excluding the cost of inbounding it and outbounding it.
A not so simple cost structure is like this:
$200/mo compensation agreement
LxWxH = 0.82 cents per cubic foot.
Cubic volume 100% of cost first month, 10% depreciation every month after that.
$2.00 handling and processing fee outbound
$0.39 handling and processing fee inbound
18% additional charge for cost of shipping
$240 for inventory returns + cost of materials.
stay away from those companies, because they are out to get you and make a profit from you not being able to profit from your inventory and knowing you will have lost your profit they will resell your items after you stop paying them for their own profit, unless you pay a lot of money to get your items back. This is because a LOT of Chinese companies set up U.S. 3rd party distribution with small low profit items, such as cell phone cases. So if they tell you "Oh, only a small percentage after a couple of fees" it doesn't sound as costly as someone who has already laid out prices.