In the far off time of late 2018, Square Enix released a couple of different package deals for the Kingdom Hearts franchise. Specifically, they released a package deal called Kingdom Hearts - The Story So Far - that included Kingdom Hearts HD 1.5+2.5 ReMIX and Kingdom Hearts HD 2.8 Final Chapter Prologue.
Essentially, this deal included nearly all of the content leading up to Kingdom Hearts 3. It cost you just $39.99...