Sata 2000's are hard to beat IMO. German Engineering. No gaskets or plastic parts to wear out to speak of. No plastic gaskets on the needle, just excellent close tolerance machining. They are sold as a set because they are machined as a set. Very close tolerances between the needle and nozzle. When they are used they wear as a set and just replacing one or the other will result in poor performance.
Keep in mind too that the 2000 series guns first came out over 20 years ago, and have been superseded by 3 generations of guns, so afaik Sata doesn't continue to manufacture replacement parts for them. I had one Sata 2000 HVLP that I used for 15+ years day in, day out. Only replaced the needle nozzle set one time. Conservatively did 1500-2000 jobs with that gun (base, midcoat). Again just my opinion but Sata makes the longest lasting guns on the market. Still have a 2000RP that I continue to use.