Work / Poland work permit and visa fee if cancelled [6]

Hi I have an offer ,I will come to Poland in August and start to work ,my recruiter asked my to send copy of my passport in order to prepare visa and work permit ,I have also second work chance in another company ,I am in 3rd stage ,this job is actually my dream job and I want to work there much ,my question is like that ,if I send them my passport and if they start to apply to work and visa permit and then suddenly i will say them I am not able to come because i have better offer ? Will it cost them a lot ? I know that it is rude :( Please help me