I load 20 ga TSS shells, and have loaded 12 ga in the past.
At the very least (equipment wise) you need a scale, roll crimper, hand drill, and some type of a razer blade. A funnel is also helpful but if you are cutting cost to the bone, you can get by without one. You can upgrade to a drill press at some point (if you want to) for around $100 (Harbor Freight) works just fine.
Cost of shot is approx $45-50 per pound depending on where you get it and who you get it from.
Depending on who's recipe you use and what components are used as well as the amount of shot your shooting (there really is no reason to go over 2 oz and most are in the 1 3/4-1 7/8 oz range) will depend on the cost of the shell. Some people do load 2.25 - 2.5 oz in a 12 but why? I myself have gone to a 20 ga. using TSS and shoot 2 loads, a 1 7/16, and a 1 5/8 oz load. Both work great and with the 1 5/8 oz load, I am putting over 300 pellets in a 10 inch circle at 40 yards.
Back to cost, just as a ball park making lots of guesses on cost, each shell is going to be around $7.50. Could be a little more or a little less depending on the components used for the load.
I will tell you this, FOLLOW THE RECIPE OF THE LOAD! I have a friend that has spent a lot of money developing loads and having them lab tested and just a little variance makes a big difference in pressure. Use the exact hull, wad, buffer, mica, and anything else called out in the recipe and use the exact amount of powder, shot and buffer as well.
It really is not hard to load these shells, and I like the fact that I know that the shell I am shooting did not change from year to year like some manufacturer's shells do, which means you may have to start all over with the matching of shot, shell, and choke matching because your gun does not like whatever it was that changed.
I have been shooting TSS for 8 or more years now and do not see myself ever going back to lead.
Yes the cost is more but lets face it, turkey hunting is not a high volume shooting sport.
When I was hunting TX and TN (both have 4 bird limits, at least where I was hunting)
I might have shot 12 shells total (limited in both states) and 4 shells to check zero on my gun.
Most years (for the last few years, I hunt my home state of TN) I might shoot 5 shells per year (4 birds and one to check zero before the season).