so just be nicer to her these days when you do up your tank.
buy her some gifts (no need to be expensive ones) buy her favorite food for her.
give her more compliments....
destroy your receipts, buy things with cash - dun use credit cards, stock very slowly....... etc etc.... dun let her know your tank expenditure.
Bring her go and buy cheap cheap corals 1st - those at SL, CF - $6, $8 etc. So she has a false sense of coral pricing.
then next time when you buy corals, she would assume it is avg $8
Need to keep wife happy else you cannot enjoy your hobby.