What is the value of a 1780 Maria Theresa Thaler?

There are a few things to realize about a 1780 Maria Theresa Thaler:

Your coin was NOT minted in 1780, the Austrian mint has produced Maria Theresa Thalers fixed at Maria Theresa's death in 1780, most likely your coin was made in the 20th or 21st century. That doesn't mean your coin is worthless it just means that your coin isn't several hundred years old. Since they are restrikes, they don't have much of a premium over silver value, today they run around $25-30 depending on silver price and the condition of the coin.