Hey,
I'm a young bird parrent and being at uni and part time work I can tell you most of my money goes to my fids. Food, perches, toys, cages.. Baring in mind parrots like greys and zones can destroy a £7.99 toy in a day.. And you can't wait a month to get another, they will get bored, scream, cry..
Food is another thing, the best "quality seed mix" isn't enough to solely feed parrots on, you have to get fresh fruits and greens, pellets, calcium blocks and supplements.
Huge cages cost a ton, and it's made worse if their for a while because not only do they get a little ratty but things get eaten up and destroyed so much quicker because they get lonely and have nobody to talk or play with.
The most expensive thing would be your time, you have to invest a lot of time into these birds. It's nothing but easy. Rewarding. But not easy.
I don't want to sound mean or anything, if you do it I wish you the best and I'm sure everyone here would help and guide you with anything you needed.
Just maybe enjoy your budgie for now?