A d.II team with a properly constructed arena and properly managed staff/scouting expenses can sustain 400-500k salary even before accounting for merchandise bonuses, which would mean they could sustain a NT guard/SF without massively crippling their team (see: Harper with Ritter, Curry when he cared with Lundy).
Yes, the hope is that someone will rise through the ranks and be able to ride the coattails of their NT trainee to the NBBA. Yes, not every team will be able to do so, and some teams will be faced with a choice to sell or wreck their club team. My primary goal is to minimize the pressure on trainers to "NT or bust" with their trainees, and thus to avoid more "Owens situations", which wind up being negative all around and can potentially cost us good trainers.
P.S. 1-2 levels in each primary is huge for a big man (secondaries being equal). Two big men with 18-18-18 will completely own two big men with 16-17-16 and it's not even close. I think you're seriously underestimating this difference.
$35k-70k salary is 1-2 levels in
ALL PRIMARIES COMBINED (17-17-18 compared to 18-18-18), not in each primary.