I think it depends on your family set up if you are of an age where there are still grandparents, if people are going to be coming as couples or if they are families.
60 is likely to be a harsh cut off
We had a few families of 4 in ours, if we had got married a few years earlier they would have been couples, or a few years later they'd have been teens that people would have been happier skipping the invite. I'm slightly jealous of the people that got married young before there was a high number of spouses and kids
My best friend invited all our university gang to the wedding when we numbered 12 spaces, now inviting that group would be about 40 odd people because we are mostly married with kids.
We did about the same number and it allowed for very few friends, we didn't have all our cousins or even all our parents siblings because we both have a parent who is one of 6. Simply inviting our parents and all of our aunts and uncles would have pushed us over.
If you've got 30 invites each, assuming a typical set up where everyone only has 2 kids .
2 grandparents
2 parents
1 sibling their husband and their 2 children
4 aunts/uncles (1 sibling of parent and their spouse on each side)
4 cousins and their families (assuming each aunt only had 2 kids, who only had 2 kids)
Boom you are over without a single friend, brides maid.
If you then factor in anyone having more than one sibling, step families, friends etc
As an aside I wonder if people think we capped the number because we wanted to have a fancy venue
We did want a fancy venue but actually we wanted people that we felt really comfortable with because I would have felt uncomfortable with a larger crowd. We wanted intimate over the venue.
We had a cut off of who we would invite for dinner, who had definitely met my wofe or who had visited our new home (within reason, a disabled aunt and people that would have if they've lived closer!)