The shipping could have huge variations. Some vendors I deal with are only willing to use express mail. For example, in the Chinese kind of ebay (taobao), the payment is send through a system similar to paypal, but the rule there is, after the buyer pays the money, the money is deposit in the payment system, but not available to the seller until the buyer confirm reception of their package. That's actually a very fair system for most buyers. But then for oversea buyers, the sellers are not willing to use low-cost but slower mail service, because that delays confirmation of reception and therefore delays claim of their sales money.
However, EMS is not always more expensive than SAL. Some venders in China (especially those located in large cities), can manage EMS with up to 50% discount, or more, depending on where they are. SAL is the government postal system and doesn't have such big discount flexibility. I believe (have never dealt with it though) in other countries with big population density (such as Japan, India and Korea), it's also possible to find discounted EMS, because there are so many EMS agents that are willing to sell more service with lower price. Of course not all vendors are willing to go through EMS agent, because they have nothing to lose buy charging you higher shipping costs. But if you spend thousands of dollors annually with a few same vendors (for example you lovers of expensive hand-made yixing or kyusu

), it doesn't hurt to ask or encourage or even urge your vendors to find low-cost, faster mailing service for you.
Besides, are there any large English speaking companies acting as "middleman" and buy goods for people from overseas? I once bought through a Chinese "middleman" company and think their charge quite worths it. Their EMS discount sometimes is even more than their service surcharge, depending on how much the goods worth. But they can't deal with English speaking customers.