I don't understand what that has to do with anything, you seem to forget the part where professional voice actors are paid per word count, different to celebrities who get just a one-time payment for appearance, and Tara Strong is hailed the most-earning voice actress for a reason and it ain't because she works more than others. If you followed Hasbro's investor calls you would also know that her high price was also the reason why Twilight Sparkle appeared less with each new season, the G5 voice actors cost peanuts in comparison to Tara Strong's ~150USD for a sentence of 4 words. Sure, the cast of the new mane5 isn't nobodies, but they pale in comparison to all the gigs she had so far. Plus considering Hasbro can afford them for talking toys, having them in the series should be no issue budget-wise.