We want to remove our tub and just make this a walk-in shower, what is the most economical way to get this done?

I did this not long ago. The contractor had to break up the tub to get it out of the bathroom. Not something we could have done on our own. We now have a beautiful bathroom with an all glass corner shower.

what is the most economical way to get this done

The most economical way to get this done would be to remove the bathtub and then install a prefabricated tub conversion shower base...see image below. This base is 5 feet long and swaps out with a "footprint" that almost always matches that of the old tub...;)

In most cases, the tile (if present) only needs to be removed up a foot or two off the tub and then the shower base installed and the wall retiled to mate up with the old tile.

Any questions, let me know, OK?

Mark