$18,000 sounds pretty steep. In my opinion, they are trying to milk you. When you get to the US, just go visit the local flight schools and compare. No need to travel somewhere to get the training you need for the conversion. $18,000 seems way too much. Or better yet, find an independent flight instructor willing to give you the training you need. In the US, you don't have to get training at an approved "FTO".
Once you get your license converted, if flight instructing isn't your thing, there are other ways to build time. If you flight instruct, you may have to move to where the demand for instructors is. But the possibilities are endless