Nothing is really cheap in Paris wealthiest arrondissement. Some suggestions still:
Le Troquet: very good menu du jour at EUR 30.
Alain Millat: famous for his confitures, but also now for his restaurant, with a talentuous English chef.
Le Café de Mars: solid (but nothing extraordinary), with typical bistro atmosphere
La Gauloise, elegant brasserie. Not so cheap.
Antre amis. Smart neo bistrot.