In a city where nearly anything is available for the right price the only way to stay competitive is to get those things that give you the boosts to keep up. In general it can be assumed a competent NPC will have the gear or spells to keep them competitive in their field.
2D is an average person with effectively no training, and no reason to be specially equipped.
3D is an average person with some training, but not likely heavily invested in the profession. If affluent enough they will have at least 1D of boosters. (3D-4D)
4D is trained enough to be working in the profession and should have at least 1D of boosters. If affluent they will likely have 2D of boosters and possibly 3D. (5D-7D)
5D is a working professional and will have at least 2D of booster gear. Most will have 3D to 4D and at this point the wealthy or those with powerful patrons will be able to have boosts for all 5D. (7D-10D)
6D is veteran level and will likely have at least 4D in boosters with the majority managing to have 6D in bonuses at least in their specialty. (10D-12D)
7D – 10D is expert and can be expected to have 4D minimum and usually enough boost to match their skill. (11D-20D)
11D or more is legendary and will always have the maximum possible boosts (22D-50D)
Some will have hard gear granting the bonuses while others will have spells and drugs. Many with a sponsoring patron will have access to the gear only in their work environment (but depending on the job that may be in the field).