Lots of interesting anecdotes here, many of which conflict with my own experiences as well as the advice I've received from numerous residents of Argentina.
First of all, DHL and Fedex are far more reliable for sending and receiving any type of international package or letter. Stuff sent via USPS will get routed through the public mail system, which employees many thieves. I sent a bank deposit from BA to a US bank a few years ago, it disappeared. The deposit consisted of a check from a US bank made out to me, whoever stole it could do nothing with it. On the other hand, I've received more than 50 packages and envelopes via DHS and Fedex with no problems, and sent about 20 via DHL with no problems.
Second, I've never had DHL or Fedex hold things or demand that I pay storage fees. If the package has a deliverable address they will deliver it. If you owe import duties they will probably try to contact you before delivery, so its critical that you provide the shipper with a working argentinian phone number. DHL and Fedex will probably want you to pay the duty in cash on delivery, however a couple of times I have been asked to pay via credit card over the phone before delivery. If your item has already shipped you need to contact the shipping company to ensure their local staff know how to get ahold of you by phone.
Third, I am 99% certain that the import duty is 50% regardless of how the product enters Argentina, but if you fly into Argentina they give you a $300 exemption. I've had a few new electronics delivered here and was always charged 50% of the retail value of the item.
Fourth, the duty applies to a wide variety of goods, but not everything. Books and most (perhaps all) printed materials are exempt, most used goods are exempt but I don't think 'refurbished cameras' are likely to be considered 'used.' I had an ereader sent from Europe to BA several years ago, the firm insisted on using public mail service, so I had to go to the post office in Retire to pay the duty and pick up the reader, however the customs official asked me what the device does and decided I didn't need to pay anything since it was going to be used for reading books. That was the official's discretion, I doubt it was something covered by policy. I know several people who've received birthday and christmas gifts from friends overseas who were all charged the duty, writing 'gifts' on the box does not seem to be an effective way to avoid avoid the duties.
Fifth, how many of you are paying income taxes to AFIP? If you're living down here and not paying any taxes other than the 21% IVA in stores I can't see how you can be so resentful about paying import duties on luxury items you ship in from overseas. Think of it as your little contribution to the country and people you've grown to love.
Finally, from an economic and social development point of view, I strongly disagree with the 50% import duty. I understand why its used, and it probably does help a few nascent industries get established in Argentina, but overall it inhibits Argentina in many ways and makes it a lot harder for middle and upper class residents and businesses to get the latest and greatest goods. On the other hand, Argentina's economic policies of the Kirchner era have led to a hell of a lot more growth than the US, Japan, or Europe has seen in the past 7 years. Or is likely to see in the next 10! I think Nestor's decision to blow off the World Bank and IMF was one of the smartest moves any emerging country has made recently. Too bad we still have a bunch of lunatics running things back up north.