Many systems are available. Most business equipment is purchased from vendors such as HP, Dell, Lenovo, Apple etc. Systems vary from low throughput to high throughput. Cheaper systems are generally slower and less capable than that at higher prices.
Custom built systems can be made for gaming which are high budget items and have superior performance.
Simple office computers still require decent performance for productivity. Going for a cheap system can prove to be regretful when wanting multiple websites and apps open at once and switching between them. Latency can occur causing frustration for the user.