I think it depended on how much you used the phone. In the 80s I think the landline for local calls tended to be about $10 or $20 a month, depending on where you lived, but long distance calls would really balloon a bill.
According to yahoo finance
"
Landline Phone Bills (and Long-Distance Fees)
In today’s society, it is common for everyone to have their own mobile phone, but before this was the case, landlines were essential within every home.
Post-WWII, in 1945, it was common for five people in a household to share one landline. Throughout the ’80s, AT&T was monopolizing the communication business and nearly every American household was an AT&T customer and rented their phone from the company for $1.50 to $5 per month.
In 1993, the government ended AT&T’s monopoly and allowed people to own their own phones. Dial phones cost around $19.95, which is the equivalent of $50 in today’s money, according to The New York Times.
Most phone companies charged landline and long-distance fees by the time of day and how many minutes the call lasted. In 1997, there were categories of plans that went from $10 per month up to $25 per month. For AT&T users with an under $10 plan, every call cost 15 cents per minute, according to a 1997 publication in Consumeraction. In other words, people with this plan had up to 66 minutes of daytime phone time per month. For those who required more talk time, they could pick plans with a higher monthly limit and could choose a plan with lower prices during the time of day they used the phone the most.
While in the 1910s long-distance phone calls had astronomical prices, prices gradually stooped so low by the late ’90s that the federal communications commission no longer tracked long-distance phone calls.
In 2018, a government survey found that a mere 5% of households relied entirely on a landline, and over half of survey participants relied on cellphones exclusively."