This just isn't true at all, all the middle class professionals I know earn about $1100-1500 a month and they get along just fine. I personally spend about $1300 a month total, renting my own one bedroom apartment for $750 a month (but this is expensive - you can get much cheaper if you sign 2 year contract) and live a very good lifestyle here living on my own, eat out basically every day, do lots of activities, etc.
$1500 USD is 55k pesos, that is enough for a very good middle or upper middle class lifestyle here. With multiple incomes, it becomes even better, as rent is less of a burden on the salary of a couple vs a single. OP says he earns $5000 a month, which is enough to live like a King. Practically no one in Argentina earns that much money unless they work in finance, trade stocks, own businesses, or are famous.
My girlfriend lives on her own in a 2 bedroom apartment in an upscale barrio in CABA, she earns $966 USD per month at current rates, and she most definitely does not live a "miserable lifestyle".