By current standards it wasn't a bad crowd yesterday. It was on a par with 2010 and 2014 and just less than 2009. It was certainly much better than crowds for other semi finals of the last 10 years.
2008 / Sturt vs Norwood & Central District vs Glenelg / Adelaide Oval / 22568
2009 / Sturt vs Eagles & Central District vs Glenelg / Football Park / 14207
2010 / Eagles vs Glenelg & Central District vs Norwood / Football Park / 13162
2011 / Eagles vs South Adelaide & Central District vs Norwood / Football Park / 11443
2012 / North Adelaide vs Central District & Norwood vs West Adelaide / Football Park / 10284
2013 / North Adelaide vs Eagles & Norwood vs West Adelaide / Football Park / 9248
2014 / South Adelaide vs Sturt & Norwood vs Power Reserves / Adelaide Oval / 13431
2015 / Central District vs Power Reserves & Eagles vs West Adelaide / Adelaide Oval / 9247
2016 / Ravens vs South Adelaide & Eagles vs Sturt / Adelaide Oval / 9029
2017 / Sturt vs Central District & Power Reserves vs Eagles / Adelaide Oval / 9029
https://australianfootball.com/leagues/every_final/SANFL/107/Premiership+season/3?season_from=2008&season_to=2018&round=all&club1=All&club2=All&ground=All&limit=1000
I think I've collated that correctly, but can't vouch for the accuracy of the figures