Well probably cost more than the 150, but not as bad as you think.

Get some R-11 and do the walls, do the R-19 in the ceiling.
I like the idea of using the pink board to create a ceiling, either nailing them to the underside of the rafters. Or just laying them on top, then put the insulation on top of that.
You want to create a reasonably airtight area, not to suffocate, but no major drafts.

What you save on propane, and frozen fingers will make up the difference REAL quick.

Maybe even for now, use some plastic to isolate and insulate just half the garage.

__________________
KLK, MCSE

1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.