De Decker – the reigning World Grand Prix champion – was heavily tipped to make the cut for the eight-player tournament, which gets underway next month.
But the Belgian was instead overlooked, becoming the first player in the competition's 20-year history to miss out after winning a major televised title.
The snub has angered 'The Real Deal', who admitted "disbelief" after not holding back on his criticism of the decision.
"My first feeling immediately after the announcement was one of disbelief," De Decker told Het Nieuwsblad.
"The past 20 years, the Grand Prix winner was there every time.
"Of course, I can't change anything about it, the PDC is boss. But I think their decision, to be honest, is a bit scandalous."
De Decker also took a swipe at the inclusion of Aspinall and Price, believing the former has only been chosen for his popular walk-on song – 'Mr Brightside' by The Killers.
"They did not deserve it. Suddenly they reach a quarter-final at the World Championships and they are there," he said.
"After my Grand Prix victory, I said that I might not be ready, and I don't regret that. But afterwards, I confirmed at other tournaments that I can compete with the world's best.
"They say that you get into the Premier League based on results, but apparently that is not the case.
"Aspinall is there with his walk-on purely for the entertainment and if Price performs badly in the first few weeks, he will start complaining again.
"It just has to be fun for the audience, be clear about that. You now get a glorious exhibition tournament of 17 weeks, nothing more."
The PDC's chief executive Matt Porter said the decision was down to De Decker not showing enough consistency, challenging him to make the latter stages of events more regularly.
"You have to show that you can compete in the latter stages of TV tournaments on a regular basis," Porter explained.
"Doing it once is fantastic and is something that you will always have but to really be part of the elite, you have to be doing it on a regular basis over multiple years."