This can be accomplished through a summary field, then passing that summary as a lookup, then using that lookup as a condition for your summary. Sounds confusing, but it really just 3 steps.
Step 1: Create a summery field to summarize the "Maximum" Record ID# from your child table. Might create a field called [Maximum Record ID#]
Step 2: Pass that new summary field [Max Record ID#] as a lookup field back to the child table. it might call the field something like [Quote - Maximum Record ID#]
Step 3: Create another Summary field of your dollar value, but make sure you place this condition; "Only summarize values when [Record ID#] is equal to the value in the field [Quote - Maximum Record ID#]
let me know if you get stuck.
