Once a Certificate of Sponsorship is assigned, the visa decision itself is usually one of the faster parts, with a priority service available at extra cost. What takes longer is everything before it: the employer assigning the CoS, your TB test appointment, and biometrics at a visa application centre.
The cost surprises more applicants than the timeline. Alongside the visa fee there is the Immigration Health Surcharge, which is charged per year of the visa and is normally paid upfront for the whole period. For a family this becomes the largest single item, so budget for it before you accept an offer.