The parts costs quoted seem reasonable. I did some speakers for my neighbour, cost about $1000, and dramatically improved every aspect of the speakers' performance.
I'm retired too, and it's my hobby too, but I'm not in the business. The posters above should be able to help you a lot.
But don't go cheap on the treble crossover capacitors. I would spend the bucks to get film and foil, preferably styrene and tin (MIT sells a good one) on the treble signal path. In this case, you get a LOT for what you pay, maybe the best bang for buck in the whole audio chain.