3PL vs SFN costs for lightweight items: what's reasonable?

[kpopstationery]

Hi, I am about to launch new store and sell mostly very light items, simple operation with 10-20 skus, and most of the orders are just multiple packs of one of the top 3 skus with weight 0.5~1lb. We will plan to manufature from china and ship to USA. At 2000 orders per month, what would be a reasonable cost per order for 3p fulfillment service and how much will it be for example 10 items for one order if I'm using SFN (reason I ask this is because cost calculator for SFN doesn't make sense to me - cost me $20 or more)