Your question was reliable and inexpensive magazines and I will assume for a full sized government type model.
If your gun is not particular, you can get away with a number of mags. If your gun has any sensitivity at all, that puts you in the high dollar mags, such as, Wilson 47 series, genuine Colt (from Brownells) or Tripp Research Cobra mags.
The best choice is Check Mate Industries. Checkmate is a gov't contractor for 1911 and M14 mags and makes mags for Colt to Colt specs. Their quality is very good. You have to call Joe DeBello at Check Mate. Don't use email. With 7 or more mags purchased the cost for a blue 7 round with hybrid or GI feed lips would be about $17 each. Note: that I specifically mentioned hybrid or GI feed lips. The feed lips make a huge difference in reliability.
I will tell you that 7 rounders are more reliable than 8 rounders.
For the cheapest reliable mags I would suggest Chip McCormick (CMC) Shooting Stars. These are $12-$15 each at Midwayusa.com. An upgrade to these are the CMC Power Mags, about $17 at Midway on sale or Natchezz Shooting Supply the last time I looked. The Power Mags are noticably better. Both are 8 rounders. These mags have wad cutter feed lips.
Whatever you do don't get "gov't type", USA, Triple K or Promag mags. All are junk.
Mags have to be tried in the particular gun to see if they work. I have some where the Shooting Stars work fine and others where the Shooting Stars are jam city.