Curiously, most ended up preferring a less readable XMR ID, leaving many common and given names available.
Maybe this is because nowadays we tend to assume the good ones online to be taken - so it's actually a great idea that you point that out! Let's see how it affects the trend.
According to my recent test, the premium was 4.7 percent compared to spot rates, hence their pricing is not competitive and Bitrefill remains without a serious contestant. There you'd only pay the ~0.5% fee for going through an instant exchange in order to have your XMR arrive as BTC.
EDIT: Now, a day later, I did another test and got percentages from 1.8 - 2.0 % which is much more reasonable.
Hint: To quickly get the hidden fees of any purchase, execute units like this:
./units.sh '<xmr-cost-at-checkout> XMR' '<EUR|USD|...>'
or./units.sh '<xmr-cost-at-checkout> XMR / <value-in-fiat> <EUR|USD|...>' '%'
for the total percentage asked.