I could have bought a Cadillac with all the money I spent on snacks for him.
この場合、次のような言い方ができますよ。
ーI could spend endless amounts of money on my dog.
「愛犬のためならいくらでもお金を使える」
to spend endless amounts of money で「無限の量のお金を費やす」
ーI could have bought a Cadillac with all the money I spent on snacks for him.
「彼のおやつに費やしたお金全てでキャデラックが買えたかも」
the money I spent on ... で「…に費やしたお金」
ご参考まで！
I would do anything for my dog. I will buy him anything and spend all my money on him.
ご質問ありがとうございます。
・「I would do anything for my dog. I will buy him anything and spend all my money on him.」
（意味) 愛犬の為ならいくらだってお金を使える。
<例文>I would do anything for my dog. I will buy him anything and spend all my money on him. Just the cost of treats could have bought me a Cadillac.
<訳>[愛犬](https://eikaiwa.dmm.com/uknow/questions/68794/)の為ならいくらだってお金を使える。おやつ代だけでキャデラックが買えたかも。
参考になれば幸いです。
カナダ 
アメリカ合衆国 
