Looks like rates via Hotels.com (and i assume other leading sites) already exclude the VAT:
You'll be asked to pay the following charges at the property:
- The 21% national VAT (value-added tax) is not included in the price, and will be charged at the property upon check-out for all citizens of Argentina. Foreigners on a tourist visa are exempt from this tax. To qualify for a tax exemption, tourists must present a valid passport and pay for the services rendered with a non-Argentine credit card or via bank transfer from another country. This tax exemption does not apply for stays over 90 days. In the case of ca