Just came back from Budapest, spent there 2 days at business trip, but managed to stay for Friday/Saturday night.
First - that's a great choice, you will have fun.
Some prices - still fresh in my mind:
- taxi airport-city centre - 20 CHF (but takes around 30 min indeed)
- whisky&coke in a clube - 6-8 CHF (YES )
- nice dinner with wine at top place 40-45 CHF
- pizza/pasta/simple food out - 10 CHF
Things to try - goulash and goose liver (maybe not together).
On sightseeing - make sure you visit Royal Palace at top of the hill on Buda side. During the day it is pretty crowded, but night view on Budapest is amazing and if you are lucky - it will be empty. I was there around midnight and had the whole place for myself :) It is 10-15 minutes climbing up to the hill and may be windy so mind the dress code and max you can afford is moderate high heels ;)
Enjoy!