It is not as cheap as it once was, but it is still very reasonable. Transport is very cheap and the trams are good, regular, clean, safe etc - it costs about a tenner - prices here, not much more for a week pass than 72 hours.
https://ztp.krakow.pl/en/kmk-public-transport/kmk-ticket-guide Be mindful that the passes do not cover the airport (unless you particularly like buses, then I think you can do it on the ticket) but the train station at the airport has a booth that will sell you a ticket, or a machine, takes about 20 mins and it is about 3 euro I think, it goes into Central station, so then you would have to get the tram down to where you were staying. Ubers and Grabs also cheap, they are a bit funny about going into some of the one way systems in the Jewish quarter, Kazimierz , so you may need to walk to a pick up point. On food, it depends what you are into eating, but most restaurants are less than UK prices, and as others have said, the main square is pricier, and very touristy. Loads in the Jewish quarter, also if you fancy a late night snack, get a zapiekanka from the main market circle. The pubs are good in Kazimierz, I like Alchemia, Singer and Eszeweria, but there are loads of other choices. Also, if you fancy a pit stop, Lajkonik coffee houses are very good, it is a chain and they are all over, but you can get nice coffee, sandwiches, cake etc. in a nice warm environment with clean loos for a very reasonable price. For sightseeing, you can walk up to the castle (for free) and it is nice, Schindler's factory is good enough, but busy, I like the pinball museum, and the main square is fab. Outside of that, the salt mines are really special, can get there by train, or uber. Not cheap to get in, and regimented, you cannot just turn up, but amazing. Have a great time x PS, it will be freezing, and also there are some tramworks near Stradom that caused us a bit of an issue when we went a month ago.