the hover hint translates kostet as "caressed"... if the personal trainer caressed more, you could understand the additional cost.
If anyone cares it's because overlap take place between kosten and kosen (caressing, to caress).
kostet is the preterit form of kosen in 2nd plural
Why "persönliche" and not "persönlicher"? Can anybody explain it to me, please?
Because there is a definite article first, then the adjective comes with the -e ending. If it was plural, would be -en ending.
The personal coach is more expensive?
is more expensive = ist teurer (adjective is teuer)
The meaning is the same, though.