There are many things that can go wrong with a piano. Regular service is the best way to avoid costly repairs. If your piano has some kind of problems like sticky keys, broken strings, or broken keys, make sure you have a qualified, experienced technician service your piano.
Do not try to fix it yourself; this can lead to even more costly repairs.
Minor repairs
Most small repairs are free with a tuning job. Any repairs that take time or parts cost extra. Time is the biggest factor in calculating the cost, most common parts are not expensive.
Key covers
Broken key covers can be replaced. Many older pianos need the entire set of keys replaced.
Broken strings
Bass strings are very specific in size for different makes and models of pianos. Bass strings can cost from $15 - $20 each plus a fee for installation. Treble or wire strings are much less expensive to replace.
Broken parts
There are many different wooden parts on a piano action. If they break and it is a clean break they can often be glued back together. Plastic parts often deteriorate with time and must be replaced when they break.
Hammer reshaping
When piano hammers get old, the strings have usually worn deep grooves in the hammerheads. This can be repaired by reshaping the hammers in most situations. In extreme cases, new hammers must be installed.
Loose tuning pins
The worst case scenario is a bad pin block. If the pin block is bad it must be replaced. A new pin block is a very expensive in-shop repair.
If the block is good it might possible to install oversized tuning pins. This is a good solution.
Sometimes there are less expensive remedies. The pins can be driven deeper into the pin block with special tools if there is enough space below the string coil. This can be done for much less than a new set of tuning pins.
In dire situations, chemicals can be used to tighten and shrink the wood surrounding the tuning pin.