I am not an Alabama fan so I do not know, nor am I interested in how their lineman have performed and how much they have made in the NFL. However, for your argument to have at least some validity, you should probably provide a comparison.
You could start by evaluating how many offensive lineman from each class make the NFL and how much they have earned throughout their career for each team. If your analysis is correct (which it might be, I don’t know), the teams should be roughly equal or Iowa to show increased earnings.
Fair and interesting questions ... so it got me to do some digging.
Prior to even doing so ... my initial response was that there is inherently an apples to oranges difference in comparing Alabama's OL development to Iowa's ... because the raw tools possessed by Iowa's guys on the OL aren't starting in the same ball-park (necessarily). Don't get me wrong ... Iowa gets great athletes ... but guys who don't necessarily have the longest wing-spans, the largest hands, the most "elite" athleticism, etc ... but Iowa guys usually do possess great athleticism, great competitiveness, and they develop almost unparalleled fundamentals and football IQ. When I did a quick look of Alabama's guys in the NFL (using the ourlads site) and then cross-referenced it to recruiting ratings ... I saw 11 guys listed for Alabama. 3 of 'bama's current NFL O-linemen were 3-star recruits, 4 were 4-star recruits, and 4 were 5-star recruits.
However, apart from my initial knee-jerk reaction ... I pushed that aside and then checked earnings the current NFL linemen from each team.
The 11 current guys on the OL that I saw for 'Bama in the NFL were: Bozeman, Brown, Leatherwood, Williams, Wills, Pierschbacher, Kelly, Cotton, Neal, Dickerson, and Hassenauer.
For Iowa, I saw 9 guys currently listed as being in the NFL: Linderbaum, Boettger, Reiff, Nelson, Scherff, Jackson, Ferentz, Daniels, and Wirfs
When comparing earnings ....
Combining the 11 guys for Alabama and tallying the average ... 'Bama guys were averaging $11.4 career-earnings (to-date) per guy. Without question, that is excellent. Furthermore, in defense of Proctor's decision, some of 'Bama's more recent OT-types were garnering some truly impressing signing bonuses (definitely attractive money - no question).
When you do the same thing for Iowa's guys ... Iowa guys were averaging $23.0 career-earnings (to-date) per guy.
A few things that stuck out is that Alabama's top-earner ... Kelly was the only guy who had a somewhat longer career in the NFL. Furthermore, when I did extra searching - only Bozeman and Kelly received extra accolades by sports-writers (from more reputable sports-outlets). Both of these noted Crimson Tide players are centers in the NFL.
In contrast, the top guys that Iowa puts to the NFL have been getting recognized in many of the "best of" lists for their respective positions. Specifically, Wirfs obviously has garnered rave reviews at OT. At OG, both Scherff and Daniels have been listed as highly regarded players (elite at their positions). Even as a rookie, Linderbaum has already been making mention on these lists for his play at C.
While guys like Leatherwood, Williams, Neal, and Wills may ultimately garner more recognition as they gain more experience ... and ultimately end up being higher earners ... that also has yet to be seen.
By performing some of the digging you mentioned ... I must concede that Alabama will certainly not leave Proctor a pauper should he succeed there. However, on the flip side, Iowa's success at producing players who are the very best at what they do ... Alabama's track record absolutely pales in comparison. Furthermore, Iowa has a better track record of producing more long-term big earners. Iowa's accomplishments are made more impressive considering that the great majority of Iowa's O-linemen were 3-star guys.