So in fact even if some noble bought his title from other monarchies, this title was not recognised in Poland.
With some exceptions. Several Lthuanian families were recognized by Polish Parliament and Polish Kings as princely families upon entering into the real Polish-Lithuania union in Lublin in 1569. They are: Czartoryski h. Pogoń Litewska(*), Radziwiłł h. Trąby and Sanguszko h. Pogoń Litewska.
As it was already said, other families - 10 or so of them - have received princely titles from the partitioning powers: Prussia, Russia and Austria, or have bought them from the corrupted Polish Parliament during the dying times of the Republic. These titles were given quite late: in 18th, 19th or even in 20th centuries. They are: Czetwertyński h. Pogoń Ruska, Drucki-Lubecki h. Druck, Giedroyć h. Poraj, Massalski h. Massalski (1775 - Sejm), Ogiński h. Oginiec, Poniatowski h. Ciołek (1764 - Sejm), Poniński h. £odzia (1773 - Sejm), Puzyna
h. Oginiec, Woroniecki h. Korybut, Zajczek h. Swinka.
Few other families were given princely titles a bit earlier but also from foreign powers, mainly Holy Roman Empire. They are: Lubomirski h. Szreniawa bez Krzyża (1595 - HRE), Ossoliński h. Topor (1633 - HRE), Sapieha h. Lis (1700 - HRE), Sułkowski h. Sulima (1733 - HRE).
There are also 10 or so of so-called families of ancient princely origin.
Other titles were also bought from the partitioning powers. This way there is one marquess family in Poland, 227 counts, 80 barons and 55 knights. Which means really nothing in Poland.
The article 96 of the March 1921 constitution said:
The Republic of Poland does not recognize the privileges or ancestral state, as well as any coat of arms, and international and other titles except for the scientific, official and professional ones. The citizens of the Republic must not be accept any foreign titles or medals without the permission of the President of the Republic of Poland.
This article was later removed from the April 1935 Constiitution though. But then came the WWII, communism and the Third Republic, which also has no special interest in nobility privileges and titles.
(*) h = herb = coat of arms