Perry Park isn't without its issues... the precinct is a complete knock-down and rebuild, none of the exsisting infrastructure is useable.
Bowen Hills stadium is over the road from Perry Park, but, Abbotsford Road is an arterial road that would require a pedestrian concourse across, similar to Milton Road/Suncorp Stadium, which would all add to the cost. Side bar Bowen Hill Station will also lose the Beenleigh/Gold Coast and Sunshine Coast lines from 2027 when CRR opens.
I'd say the other element is Ballymore is marketed as a training/community/stadium facility, whereas Perry Park is exclusively a stadium aimed almost purely at football, which plays a political aspect as well(for better and worse).. Cost wise for Perry Park you're looking at $250 million minimum for a boutique 10-15k stadium, which is largely taretted at a sport/team which currently draws 5k on average to Suncorp.