Austria is a member of the European Union, and parcels sent from member countries are not subject to any taxes or duties.
The FOB valuation method means that the payment amount is calculated only from the value of the imported goods.
Customs duty
From 0 to 17%. Some goods are not subject to customs duties (for example, books).
Sales tax
20% of the FOB amount.
Threshold for duty-free import
Parcels with a FOB value of up to 22 EUR (≈23.4 USD) are not subject to customs duties or sales tax.
Parcels with a FOB value of up to 150 EUR (≈159.5 USD) are not subject to customs duties, but are subject to sales tax. Parcels with a value above this value are subject to both customs duties and sales tax.
Also, on the website of the Austrian customs service there is information that parcels from a private person, to a private person received without payment of any kind and with attachments for private use in the amount of up to 45 EUR (≈47.9 USD) are also not subject to any taxes and customs duties. The author of the project does not know any exact recipes on how to make your shipment look exactly like this. I can only assume that if you fill out all the forms by hand, put some signed greeting card in the shipment, then it might work.