Irexently purchased a home built on a concrete slab
It has a shower /tub como, but I would like to move the toilet to the other side of the room and put a shower where the toilet is now. It this doable and it it very expensive?

You can do almost anything with enough money. And being you are on a slab this is going to get very expensive in the pipes and drains aren't where they need to be... something that's not a huge deal on the average house... but it is with a slab because you will basically have to cut through the slab.. run the new stuff.. and pour fresh concrete and that's go to set up enough before you can even think about the rest of the work starting.

So #1. This will be expensive... and #2 its not going to be a do-it-yourself. Unless you do that kind of work for a living... but I assume you don't.

It will cost significan'tly less to redo the bathroom keeping existing locations...

Doable-Yes, Expensive-Double Yes.