Just like anything else in cycling, trying to figure out which bike computer will fall within your budget constraints while offering the features you prioritise can be a tall order.
Depending on how much money you have to spend, your GPS computer may have base maps, interval timers, in-depth power metrics, a colour touchscreen and more connectivity than you can shake a stick at, or it might be a simple, compact unit with a black and white display and basic training metrics.
If you have a hard budget, then you may need to compromise on some features. Conversely, if you have a prerequisite list of features, then make a checklist and see which of the best cycling computers meets those requirements, then weigh up the decision with price as one of the deciding factors.
As mentioned above, a smartphone app provides a cheaper alternative to a dedicated cycling computer.