You want a bit more noise from your bike, and have been looking at some after market exhausts systems, and got lost in what is on offer. Then let us explain the biggest difference is whether you go for an end-can of full system. Unless you've looking for big power gains, the cheaper option of just the end-can would be best for you, most bikes have stainless-steel down-pipes anyway.
Looking just at end-cans, some are four or five times the price of others. Really cheap ones may have internals that are generic while the top-end ones will be designed to suit your bike, so perform better and are less likely to cause engine problems. Materials and construction are another area where price shows.
Cheapies will be far more likely to corrode or just disintegrate. Top-end products will last pretty much forever and, if required, can be taken apart to be cleaned and re-packed.
Expensive exhausts are lighter thanks to more costly materials like titanium. Road exhausts tend to be a little more price that race ones as they have more baffling so are more complex and require more materials to make. Those with a removable baffle will cost more than those without, too, for the same reasons.
So, what do you go for? If you just want a bit more noise, go for a low to mid-price end-can from a reputable manufacturer. Yoshimura for example. Stainless steel is cheaper and more durable than carbon and Titanium.