My medical treatment cost more than I thought it would.
My hospital bill was more expensive than I thought it would be.
この場合、次のような言い方ができますよ。
ーMy medical treatment cost more than I thought it would.
「治療費が思ったより掛かった」
medical treatment「治療費」
ーMy hospital bill was more expensive than I thought it would be.
「治療費が思った以上に高額だった」hospital bill「病院代」
ご参考まで！
カナダ 
