If your sole goal is an economical upper then yes you can build one cheaper if you remain disciplined to your objective. It's real easy to start splurging. That being said you can certainly build one cheaper that'll work well for you, but it won't be to the quality of an AA upper.
If you intend to use 90% the same components as the AA upper, you'll end up spending the same you would have if you bought one from AA, plus or minus 5%-10%. That being said, if you enjoy working with your hands there's something incredible rewarding about building your own rifle.
If you know exactly what you want and you're just going to eventually modify the AA upper into a completely different upper, just build your own now exactly how you want end. You'll spend significantly more money now, but you'll save money in the long run.
If you intend to use 90% the same components as the AA upper, you'll end up spending the same you would have if you bought one from AA, plus or minus 5%-10%. That being said, if you enjoy working with your hands there's something incredible rewarding about building your own rifle.
If you know exactly what you want and you're just going to eventually modify the AA upper into a completely different upper, just build your own now exactly how you want end. You'll spend significantly more money now, but you'll save money in the long run.
"Those who sacrifice liberty for security, deserve neither." Benjamin Franklin