Please do not give out misinformation. You only need Tales of the Adventure: Stormblood to get straight to Shadowbringers. You do not need the other two.
So $25 + $25 for a class boost is actually $50 (when it’s not on sale)
Another thing you might want to keep in mind is that you only get ilvl 148 gear (they couldn’t even at least give you Korthia gear!) with a level 60 boost as opposed to getting a full set of gear that will last you to level 75 in FFXIV. Plus you have no renown and reputations are not account wide if that is something you want to pursue. Oh and not to mention, in FFXIV you can play ALL CLASSES on a SINGLE character so you don’t need to go back and start all over when it comes to character progression. This means if you were to story skip, you’d only have to pay that one time plus the class of your choice. Every class after that is just a flat $25 when it’s not on sale.