Try:
<input type="text" name="#client_id#_Fee" value="#form["#client_id#"_Fee]#">
As a proof (that we are understanding what you mean), this produces the 1000 you seek:
<cfset form.101_Fee = 1000>
<cfset form.client_id=101>
<cfoutput>#form["#client_id#_fee"]#</cfoutput>
That said, when things get so convoluted, it's usually time to start reconsidering the design choices made for those form fields. But until then, this use of array notation to refer to a variable name built dynamically is a common solution for such challenges.
Let us know if that works for you.