champagne taste on a beer budget
Expensive or extravagant tastes or preferences that are beyond one's economic means. I only earn minimum wage, but I can't stop buying designer clothes and eating at the best restaurants—I guess I've got champagne taste on a beer budget!
shoestring budget
A budget or allotment of resources that is very meager, sparse, or just enough to suit its purpose. Unfortunately, due to government cutbacks following the recession, our department has had to produce the same levels of work on a shoestring budget. I did all sorts of traveling with just a shoestring budget when I was in college. You learn very quickly how to make the most of what you have!