My impression is people love to discuss other people's money. In JA's England although there were indeed love matches, people still often married for money.
In sociey, people loved to estimate other people's worth in quiet social converse- 'how much his property's worth',
how a new gentry family made it's money, etc.
Sometimes, you could made 'enquiries' e.g an acquitance or friend on the supposed dowry of a woman or how much a man was worth i.e his annual income. (In Meryton they know Bingley's money as details of his yearly income were probably registered with a local attorney and then gossip spreads. )
Often, people's incomes was idle social chit chat.
Generally, a young woman required at least £10,000 to be regarded an heiress.

Interestingly, Miss Grey with her £50,000 dowry is the wealthiest heiress in JA's books. Although we know nothing of her parents nor are family connections mentioned.