You can find paper shredders to suit all budgets, but expect to pay significantly more for heavy-duty machines, compared to those designed for light use.
Basic Micro-Cut Shredders:
These can cost as little as $30 to $50, but the most inexpensive models will have extremely short duty cycles and will only be able to tackle a small amount of sheets per pass. Some are so compact you have to fold a sheet of A4 paper to fit it in.
Basic Cross-Cut Shredders:
These cost roughly $20 to $30. Even basic models are likely to take on more sheets per pass and have longer duty cycles than micro-cut shredders of a similar quality. Many can also deal with CDs and credit cards.