I think it depends on many variable as to where gas checks are cost effective for an individual or not,your type of shooting,hunting and economics will most likely dictate where it's cost effective or not. The equipment plays a big part in cost,you can buy the more expensive custom or iron molds or you can buy the less expensive Lee molds.
I have all three,one custom two crimp groove 38 cal. GC HP mold on order for NOE,two Lyman 38 cal. molds I bought at a yard sale for $25 each one set of blocks had the handles with it and I also have ten Lee molds from various pistols and rifles some are GC and some are not. Of the one's that I currently own all have produced good quality and accurate bullets,on a side note just because the mold is designed to cast bullets that take a GC doesn't mean you have to use one on the bullet. Several of my plinking and med velocity loads shoot just as accurately with the GC left off and no leading.
What the GC allows me to do is shoot a much softer alloy such as a HP or FP for expansion purposes at a much higher pressure and velocity than I normally could if it were a plain base bullet of the same alloy,leading can be caused by many variables but when it comes to high pressure and high velocity loads combined is where the GC comes into play,it helps seal the bore and protects the bullets base. My 7.62 x 39mm cast loads I run in my SKS rifles run at an average MV of around 1900+ fps. my 30-30 170 gr. RNPF hunting load 30:1 Lead/Tin alloy run up close to 2100 fps.
As far as a sizer,lubricators go you have several options for lubing and sizing bullets,the Lyman,RCBS,Star lube size are more convenient and less time consuming if time is an issue but they cost more. For me personally I find tumble lubing or ranch dip lubing my bullets,applying gas check and sizing bullet using the Lee sizing equipment suits my needs. I make my own lube using Alox and Johnson's paste wax and it works great and I've had no leading issues at any pressure and velocities I shot my cast bullets at. Some individuals pan lube there bullets,I've done that as well with excellent results. My budget pretty much dictates the process and equipment I use but I feel like I turn out some good quality accurate bullets.
Here are three GC bullets I ranch dip size and GC using the Lee sizers.
On the cost of GC bullets vs. jacketed in my case there is no comparison. To be fair I've pretty much have gotten all my lead alloys for free just by scrounging around over the years and being blessed with good friends that know I cast that bring me lead which I return the favor by casting them some bullets. So if you throw in the cost of the check and other materials on average you could say my GC bullets any caliber cost me about 5 cent each to make. If I add up the component cost of say my 30-30 hunting loads it cost me about $2.60 cents for a box of 20 rds. of 170 gr. RNFP GC ammo that will so the same thing as the cheapest 30-30 factory ammo will at $13 per 20 rds. Of course you have to invest in the necessary equipment to produce ammo that cheap but at some point you will realize the saving especially if your paying $20 to $30+ per box of 100 J bullets.
For the ranges and game I hunt and shoots at seldom over 200 yds. usualy 100 or less mainly due to geographic J bullets are just not needed,I have jacketed bullets in all caliber I shoot but they just sit in there boxes for a rainy day.
