Yes the 7mm Mag likes its powder at 70. g approx per shell and there is 7000g in a pound at avg $35 per pound its easy to figure, and $35-50 bucks per hundred bullets as well $3-6 dollars for primers. You can use the cheeper reloading supplies but it will reflect on the end result at times. But I always figure about 70-75 bucks per hundred shells and i do not count the brass its a one time deal.
As for equipment you can buy a nice starter kit RCBs is better than the lee, but the new lee cast press is every bit as solid as the rock chucker.
I think you see mostly rock chuckers or lee presses in most of the basements i have been in for startes, Hornady 007 is a great press as well but $$.
If buying individualy go with the new lee cast press, I bought on to try it and i have to say my other presses do not get used as mush its small accurate and very solid for about $150.00. Lees Kit press sucks dont go with it its a bit flimsy but ok for seating bullets.
Kits run from $280 to $400 plus I would slide up to the $400 RCBS and you get what you need. like pocket cleaners and a basic trimmer some small tools and a scale. I started off wih the basics years ago and it worked fine.
Dies run from lee about $35 to RCBS $60-80 and up for others.
I would allow $650.00 to get going on one caliber to start off.