I’ll share my setup for transferring dollars from the US to Argentina en blanco as a monotribuista that I've been using for the last few months:
In Argentina, Santander offers free peso/dollar accounts as long as you make at least three transactions per month. According to comments I've read online from Argentine freelancers, they also have the least complicated process for receiving SWIFT transfers. Today I wired $1000 USD from the US and received $1000 USD in my Santander account, minus just $2.42 USD that they subtracted, in pesos, from my peso account. According to their fee calculator (visible for clients on the website at Menu | Cobros del exterior | Calcular comisiones), they are currently charging $2.42 USD for amounts up to $1,000 USD; $7.56 USD for $1,001; $39.32 USD for $10,000; and $393.25 USD for $100,000.
In the US, HSBC offers free wire transfers for Premium customers, which you can get if you can transfer and maintain $100,000 in cash or investments, plus they'll pay you a $1,000 sign-up bonus.
The process for sending money is straightforward: I log in to HSBC, initiate the transfer, and download the receipt as a PDF. A few hours later, Santander notifies me that the transfer is ready to be liquidated. I then log into my Santander account, go to "Cobros del exterior," attach the HSBC receipt, and attach proof of the source of funds (in my case, a sales invoice generated through ARCA's monotribuista portal). By the end of the day, the dollars are in my account.
Once the dollars settle in Santander, I transfer them to Cocos Capital, which offers a 4% APY on dollar balances invested in their "Dólares Ahorro" fund until I'm ready to convert them to pesos. They also pay 32% for pesos in their "Pesos Daruma" fund and provide competitive rates for currency conversion. As of today, with the official MEP at $1,280, Cocos will sell your dollars for pesos at $1,273.49.
So, starting with $1,000 in the US a few hours ago, I have (1000 - 2.42) * 1273.49 = 1,270,408 pesos in my account today, which beats Western Union and MoneyGram, although it does require you to qualify for HSBC Premier to get the free wire transfers.
Alternatively, someone mentioned in another post that Macro Bank has removed all fees for dollar transfers, which could be even cheaper, but their handling of SWIFT transfers may not be as user-friendly as Santander's.
I'm pretty happy with this setup, but am very interested in hearing about what everyone else is doing!