Dealing with lawyers is a cow-milking process. After each procedure/application, there will always be the next one (usually even more expensive). This is why once I got familiar enough with the HC process (after two failed applications you sure learn a lot), we cut ties with lawyer and did not go with the next stage she offered (a 10K+ federal court appeal). We submitted our own HC and it worked.
Many people think you need legal background to win HC. You do not. You just have to be diligent with your paperwork, fill out correctly your application forms and structure very well your HC arguments with proofs (with good boring bureaucratic English). In our last application, I did not have a single legal argument. I removed all legal arguments that lawyer included in previous applications like examples of similar cases where judge issued a favourable decision. Clearly, previous officers did not care much about those since we failed multiple times.
all this to say: listen to lawyers advice, if you wish and you can afford, but don't think they are holding some sacred keys to heaven and don't jump into writing them their next cheque. Many of us did it on our own. My humble advice as someone who saw people burn their life savings into lawyers.