I had a spreadsheet built up from asking people and lost it. It's about 80k sapphires, if you are happy trusting my memory :)

The cost doesn't go up that much per level, ends of something around 12k/13k per level.

Thank u man

I had a spreadsheet built up from asking people and lost it. It's about 80k sapphires, if you are happy trusting my memory :)

The cost doesn't go up that much per level, ends of something around 12k/13k per level.

Sounds about right.  You're probably better off just using the sapphires for troops though, doing big hits you'll get the hero fully upgraded pretty fast.