我也碰到了楼主所说情况，打算在当当上买三百多块钱的书，结果发现居然还要付邮费，甚至在一定的价钱范围内，反而每单费用越高，邮费越高！让人很抓狂啊！查了半天也没想要的答案，问过当当客服才知道，是否免邮和下面音随有关（我的是因为第一条，如何区分见这里zhidao.baidu/link?url=m6PY0kVrnJyLk4i3cSVGwXJ4oF4AGQ8XOFkJNP2pXbqQBECckFmYTFXi-mGEe0TmWp6T_xMelECTMJNpcW2rng0JeQKD0Cep7hJETmm_hgi）
下面是当当客服回复
您好，当当包邮政策：订购当当自营商品，全国（除西北五省）普通快递送货上门和平邮订单，每单满49元以上免运费，西北五省（新疆、西藏、甘肃、宁夏、青海）每单满59元以上免运费，不足以上免运费标准的，每单收取5元运费。
如您的订单未包邮，原因如下：
1、订购的商品为商家商品（商家商品运费有商家收取，不在免邮政策范围内）。
2、订购的商品金额未满足当当包邮政策标准。
3、选择的送货方式不是“普通快递送货上门”和“普通邮递”。
最后，如果楼主是买书自己看，而且不要求全新的话，可以去孔夫子旧书网看看，那里有很多二手书，价钱便宜而且质量也不错。
希望能帮到你，欢迎采纳！
FCTY ADVD GOODS WIL BE RDY BY 7/15 N WIL FAXUS BREAKDOWN TMW,WIL SEND U BKG ADV N WIL ADV N WIL ADV UPDATED O/F
Factory advised that goods will be ready by July 15, and will fax us th breakdown tomorrow. will send you the booking and will advise the updatd ocean freight... （乱七八糟)
大概意思：工厂告知这批货会在7.15前备妥，明天会发给我们明细。明天会发给你订舱信息以及最新的海运费。
INFO NOTED NCNEE RE-CFMD THTA THIS CGO WIL NEED TO SHIP VIA SEA-AIR N VNDR WILBE RSPNSBL FOR O/F DIFF.PLS MAKE BKG W/AIR-SEA AS CNEE HAS ALRDYAPRVD TO SHIP THISWAY....JUST PASS BKG DETAILS FOR CNEE'S INFO ADVG SEA/AIR SKED CGO WIL BE SHPGVIA .ALSO PLS ADV ALL COST DETAILS SO CAN ADV U AMT OF O/F DIFF TOCOLLECT FMVNDR
Info noted and CNEE re-confirmed that this cargo will need to ship via sea-air and VNDR will be responsible for ocean freight difference. Please make booking way of air-sea as CNEE has already approved to ship this way... Just passing booking details for CNEE's ....（翻译不下去了。。。）
大概意思：邮件收悉，CNEE 再次确认这批货需要通过海空联运的方式运输，VNDR会承担运费差价。请按照CNEE的指示订舱，你就把船期表和航班表发给CNEE就好了。请告知所有费用明细，以便告知你运费差额，以便你去向VNDR收取。
VNDR IS STILL WAITG FR CNEE TO OPEN NEW L/C OTHERWISE THEY CANNOT SHIP IT N WON'T FAXSHIPG DETAILS.LOWEST SEA-AIR ALL-IN RATE IS U＄5,707.50/40'.
VNDR ALSOADVD GOODS WIL NOT GET READY B4 7/20.
VNDR is still waiting for CNEE to open new L/C, otherwise, they cannot ship it and won't fax the shipping detals....（这段应该不难理解吧）
大概意思是：VNDR还在等CNEE开出新的信用证，开出来之前，他们不会发货也不会传真过来订舱信息。海空联运最低价格是5707.5美金/40尺大柜。VNDR还告知，货物得至少7.20才能备妥。