Hello Composers, Mike here. =)
The piano is in my opinion, the most fundamental instrument of all time. Simply because the sound itself is timeless, and because the piano can be used in practically every style of music ever created.
The piano also comes in different shapes and forms, such as various grand piano models to upright. And they can be recorded in different ways, with different microphones etc.
Recording pianos and scripting and creating a piano plugin or sample library takes a lot of effort. Not as much as an orchestra, but the end product can still be expensive.
However, I have found these great and free alternatives for you: