FA Cup prize money was 2.295 million plus about 800k in TV fees for rounds 3,4,5 and 6. Don't know what the fee was for the semi-final, if there was one.
These figures don't take account of matchday profits (or losses).
Reached the QF the previous season, so don't think there will be much incremental advantage (especially as in 2018 QF was at Old Trafford instead of The Den).