"Balking at the $50+ charge for turnkey assembly, I opted to take the financially responsible route and pay $200+ for a hot-air rework station to solder it myself."
This statement also hit home for me when I thought over my woodworking tools. I could buy finished timber for $300, or I could spend $500 on tools and several hours to finish $75 of rough-sawn timber myself.
Almost never, in some cases you can but you need to be really in a nice and usually have access to the tooling for XYZ reasons. Then you would need to factor your labor cost, which is usually more than what would be billed normally in some cases...