Complex sentence: Originally, "Sincerely Yours" was meant to be the first of a two-picture movie contract, but it was such a financial disappointment that the studio bought back the contract, effectively paying Liberace not to make a second movie.
Split into simpler sentences: Originally, "Sincerely Yours" was meant to be the first of a two-picture movie contract, but it proved a massive box office flop. The studio then bought back the contract, effectively paying Liberace not to make a second movie.