Some ~40 years ago, I started out pretty cheap and only used cast for 38/357 plinking ammo.
After the discovery of powder coat, I now shoot 100% cast for everything bigger than 0.224" (including magnum pistols and bottle neck rounds in Contenders).
I really like shooting about once a week for an hour or two per session. I cast for myself, my son and a friend. I could not justify this volume of shooting without casting.
At least one decent reliable lead source is needed. At one outdoor range I get 2 or 3 opportunities per year to gather a couple of 5 gallon buckets of range lead (no cost, but lots of effort to sift from the loose dirt at the range and then process at home). I have also resorted to buying scrap lead from a big metal recycling center at $1 / lb or so. It is mostly too soft (pure) but much less effort. There are a few small timers that do a decent job supplying lead to bullet casters through the mail, but the shipping does add to the cost.
For someone considering casting, check out Titan reloading for Lee products. A Lee 10# or 20# bottom pour pot, a couple of Lee two cavity molds and some Lee liquid lube are reasonable first investments than can get you up and running for about the price of one mold from other makers.
The next step up IMO would be Lee push through sizers (as needed, if needed) and Powder Coating (PC).
I had my wife shop for a used toaster oven and got set up to use PC for not much. I later upgraded to a PID temperature controller and still have less than $70 invested in PC hardware.
For someone new, I recommend starting with revolver ammo or 45 Auto ammo. Probably buy some cast bullets first, find something you and your gun likes and then move into casting. On the other end of the spectrum, 9mm guns can be really hard to please and the 9mm is probably the worst to start with.