programming by hand

It would only take about 40 hours of writing G-code "by hand" to offset
the cost of a decent CAM package. That's about 2000 bucks at average
billing rates.
Anything but the most rudimentary code writing would quickly run into
labor cost that would far outweigh the cost of CAM.
If your controller won't take a floppy or RS232 or whatever then that is
another matter, but then you probably need to upgrade the control. The
same amortization would apply to the control upgrade.
It just depends on how you cost out your time. Most hobbyists don't
bill their time as money, so a few hours of code writing is cheaper than
500 bucks cash money.
Still, it is awfully inefficient with all the stuff available.
My $.02