I think the range between 1 and 30 people would be significant. Say with 3 people, I'd say the owner's income would be doing really really well to be double what they'd pay a staff accountant level position (so, if it's in an area where that'd be a $60k job, the owner might be making $120k), unless they're working completely absurd hours. That's assuming 1 owner, 2 staff-level employees, so the owner makes about $60k off the work that s/he does and about $30k off the work each employee does. Pretty good, honestly, and probably over-estimating.
The more employees, the more of the owners' time has to be spent managing and overseeing and the less working. So, it doesn't scale up at $30k or half of the employee's wages per employee (and $30k is probably a high estimate anyway). A 30 person firm, I'm not really sure, but I'd think Mayo's $200-250k is probably pretty reasonable for a successful firm.
Keep in mind that my figures for both 3 and 30 people are for firms that are doing well. You'll also have 3 and 30 person firms where the owner's or partners' income is $10k, or even $-10k, depending on how well the firm is doing.
.