Not only was the Chandrayaan 3 budget lesser than that of Chandrayaan 2, as a meme doing the rounds point out, it was lesser than the budgets of some Hollywood blockbusters like Interstellar. So yeah, safe to say they could have had the budget for more if necessary.
"Fuel budget", "mass budget", "payload budget", even "delta-v budget" are common terms in spaceflight and refer to how much of a valuable thing a spacecraft can carry given some pesky laws of physics [1], nothing to do with money (except insofar as more money would let you build a bigger spacecraft…)
