It's important to realise that the only situation where RAM usage matters, is if your system does not have enough RAM installed. Many people don't understand that and think that RAM usage is an indication of how light an antivirus is, which is simply not the case. I use many different antiviruses and never check the RAM usage of any of them.
If you can't afford to upgrade your system, then RAM usage will matter to you. But having said that, you can buy used RAM for very little on eBay.
when you only have 3 gb ram, most antivirus will kill your system. i have a blog where i used to write a bit on what to use for those with older systems to keep them humming and relevant, and i'd get a lot of people from india and africa that were very interested. if you live in the poorer area of india and make (lets say) 200 dollars a year, i think you'll find that those ebay prices are a bit high. ram matters for them.
myself, i have several computers, some very good, and some that suck, and the ones that suck illuminate to me an entire other world of problems in regards to what constitutes good software. i have an old 2nd gen tower that was approaching rigor mortis, lol. the bottleneck was the ram. so i paid a hundred or so and jumped that to 16 gbs. now the ram is good. butttttt ... now i see a new bottleneck. the hdd is struggling with Mcafee. who knew that Mcafee would be so friggin read and write happy, so that it consumes 100% of that resource? interestingly enough, other AVs are far lighter in this regard, so that my system works perfectly with them. I might throw an sdd in and jump that hard drive speed by 5 fold to fix that, but that doesn't negate the fact that not all software is made equal. my old system helps me see which companies are simply smarter at engineering and writing effective, clean and light software. i will continue on with my holy quest to battle that monsterly beast called
planned obsolescence, lol.