They go silent, or they also give a canned response about being competitive in the market when it comes to comp (without naming a number).
If they do name a number and you reply it's too low, they again go into a canned response of "we're willing to reach (++x) for the right candidate", which is just as much bullshit as before. You'll complete an interview cycle and get the lowball offer of (original x).
TLDR they'll lie about comp and never completely answer you.
Sometimes I say something like "I'm glad to hear you're competitive! I'm currently being offered $REAL_BIG_COMPANY_NUMBER, so I look forward to our conversation." Generally this ends the conversation.
If they do name a number and you reply it's too low, they again go into a canned response of "we're willing to reach (++x) for the right candidate", which is just as much bullshit as before. You'll complete an interview cycle and get the lowball offer of (original x).
TLDR they'll lie about comp and never completely answer you.