You'd have to burn around 7.5BTC to fully exhaust everyone's mempool
And let's not forget that if some crazy multi-millionaire ever thought of executing this meaningless attack, nodes could just adjust the mempool size limit and make it ever more costly to do it again.
Anyway, the fact that it costs 5 digits to pull off a successful mempool spam attack for no material gain shows how strong Bitcoin (and the Bitcoin price in particular) has become.
It also shows that the block space is expensive. If block size was 10 MBs, spamming the UTXO set (or blockchain in general) would be about 10 times cheaper. See what happens with BSV, where they have 1 GB blocks, and some even store movies in.