MIAMI BEACH, OCT. 2 -- At 85, Bill Sussman spends his days under the palm trees, cooled by gentle sea breezes in a tropical setting that would be the envy of his friends back in New York.

The irony is that the scenic vistas that lured Sussman to Florida in 1968 did not turn out to be paradise. He lives alone in one of the pastel-colored hotel buildings that line the avenues of Miami Beach, and he tries to survive on $455 a month from Social Security and his pension fund.

Miami Beach has one of the largest concentrations of elderly residents in the state and also one of the poorest. Here, in the muggy one-room efficiencies, is where an increase in Medicare costs would be felt most acutely.

"It will hit me very hard," Sussman said quietly. "It will cut off a lot of things that I could buy."

Sussman's income hovers just above the federal poverty level, although elsewhere in his neighborhood some other elderly people fare much better. That is another paradox of old age: Medicare affects all elderly equally, regardless of financial status.

Under the proposed plan, the annual deductible, which covers visits to the doctor and outpatient hospital treatment, would double to $150 in 1993. The cost of the monthly premium would increase from $28.60 to $33.50 next year, the price of a movie ticket, and to $54.30 in 1995.

Such increases may seem minuscule to others in more fortunate circumstances. But Sussman, like others here, measures his purchasing power in equally small increments.

His life is caught up with what might appear to others to be the little obstacles, such as how to carry his groceries home now that he no longer has the strength. His major purchase this fall is not a new automobile or a vacation trip but a new tank for the toilet in his condominium.

"These are people for whom every dollar makes a critical little difference," said Yvonne Lee, director at the Miami Beach Senior Center.

Already, the center has held a session on the proposed increases to Medicare premiums at its Current Events class. Sussman, like others who have discussed the proposed increase, does not speak in angry or accusatory tones about what the government may do to his standard of living. He is far removed from the fiery rhetoric used by lobbyists in Washington to dramatize the effects of the budget axe.

Instead, Sussman and his friends worry. There is not much they can do, they said. By Sussman's account, he is unable to absorb such increases, even when they are as small as the price of a movie ticket.

The electric bill, he began, is $15 a month. He is almost apologetic about this, explaining that the refrigerator and hot-water heater run all of the time, as if he has considered turning them off. Then he added that he cuts back on the air conditioning to keep the bill low. Sussman described this as the temperature topped out at 89 degrees, with near-equal humidity.

Sussman's phone bill runs to $30. Maybe he could trim that, he offered, because he occasionally calls his sister in New Jersey to see how she is.

Sussman lives rent-free, thanks to a friend who died 10 years ago and who had written into her will that he should remain in her condominium for the rest of his life.

But every three months, Sussman must pay a $230 condo maintenance fee. Blue Cross charges him about $90 a month for health insurance, which with Medicare covers most of his medical bills.

He tries to get by on $30 a week for groceries, but sometimes cannot. After these expenses, he has about $125 left for the rest of the month.

From that, he must pay all of his household repairs at the condominium. Right now, he is facing a plumber's hourly labor charges and the new toilet tank.

"I skimp on everything," he said.

Every day, he goes to the Senior Center, where most of the classes and activities are free. He eats lunch at a nearby school that operates a subsidized hot-meals program, and he donates 75 cents every time.

Sussman still strolls occasionally under the palm trees on the sandy beaches. And he said he still likes to dine at a restaurant, although these days it usually is McDonald's.

"I got to eat where it's cheap," he said.