The cost of taxi depends mostly on the number of kilometers driven. The price for 1km in Wrocław is generally 3pln or a little less. You should add to it the boarding fee - 6pln.
Witam! Yes, it seems more expensive than in Warsaw but I remember some years ago, taking a taxi was more expensive in Katowice than in Warsaw because .... less competition. It could be the reason why more expensive elsewhere.
PS: As I don't take taxis in Katowice any longer, I don't know what current situation is but some years ago, it was more expensive than in Warsaw.
PPS: some years ago, I was regularly taking taxis from Serkieniwice train station for a 20-minute ride and then back and each time it cost 100 ZL. If less competition, it is logical than it is more expensive and most probably there is less competition in Wroclaw than in Warsaw, hence higher fare.
It has of course nothing to do with competition but I remember than some years ago, a bus/tram ticket was already over 4 ZL in Katowice whereas it was still 2.20 ZL in Warsaw (now over 4 ZL too). What I mean is that it is not - always - more expensive in the capital
A quick look on the internet shows a few between 2.25 and 2.50 per km (plus the initial 4.50 to 6zl). This is more or less around the Warsaw rate except in Warsaw you don't get as cheap as 4.50 for the starting price.I did notice a company that was more expensive.
Here's a price list, firm by firm for Wroclaw: mmwroclaw.pl/artykul/radio-taxi-wroclaw-sprawdz-ceny-taksowek-we-wroclawiu,2886912,art,t,id,tm.html