I think the views of ST holders get misrepresented here. From my point of view, I would not kick off or be angry if walk up prices were cheaper. I don't think many would, and I don't think this is the club's rationale.
I would, of course, make a cool, rational review at the end of the season and consider whether it was still economically worth my while being and ST holder. For me, it would be, as I want to attend the matches, but for a few thousand, it wouldn't be worth it any more and they'd become match by match fans instead.
Cheaper match tickets are an incentive to not renew.
Big crowd does not = good atmosphere.
The crowd being really up for it = a good atmosphere.
Often, it also results in a big crowd, but the big crowd is the effect, not the cause.
Some of the worst atmospheres I've experienced have were smaller matches during the ST sellout era: 0-0 draw vs Wimbledon, for example. That last home match in 2015 when we knew we couldn't get automatic promotion for another.
If we'd given every fan at the Spurs match a free ticket for the Luton match 4 days later, it would not have recreated the atmosphere.