Home roasting for me isnt about the possibility to save money, it is more about getting to know more about coffee in all its forms. I think I end up about square financially. Typically I would pay between $32 and $45 a kg for freshly roasted local beans. When I buy from someone else Im getting:
Hopefully well roasted beans with appropriate equipment.
Someone elses expertise, knowledge, experience and time.
Green beans you could say average around $8 per kg. You lose approx 15-17% of that weight during the roast so maybe $9.35 would be a closer average cost of green beans. Still a lot cheaper than roasted. Then you need to roast the beans so you buy a popper or a heat gun or a bbq drum. I use one way valved bags that cost approx $0.50 for each 300g I roast. So the cost of kg roasted is out to $11 give or take. Still cheaper. Here comes the the biggest cost... your time. If you have plenty of spare time then it probably doesnt matter too much, but if you value your time it can be expensive. In one session I usually roast 4 or 5 300g batches (HG). From start to finish that would take me approx 2hrs and I end up with 1.25kgs of roasted beans so $11ish (not counting electricity and cost of HG) for the beans and bags plus whatever your time is worth. Even at a measley $15 an hour youre looking at $40 or more per kg of finished product and hopefully youve done a decent job and the coffee tastes good. I have blown through a fair bit of coffee testing and rejecting blends and beans varieties.
I suppose if you had a roaster that could handle a kg or more you could get away with one or two roasts and reduce the time taken...
Bottom line it probably isnt the money saver that you might think, but the freshness and hopefully quality is guaranteed. I also get to try lots of interesting coffees I might not otherwise be able to.
I see it in terms of a hobby or interest, not something I do to save money.