FRANKFURT, West Germany (AP) _ When an American bought a Big Mac at a McDonald's restaurant in Frankfurt in December 1985, he paid the equivalent of $1.64. Two years later, the American has to spend $2.54, a 55 percent increase.

Consumers with dollars, whose value has dropped from 3.46 marks to 1.61 in the past two years, have found they have to exchange more and more into German marks to buy goods here.

As a result, a pound of prime beef now costs $5.63, compared with $3.63 two years ago. Top-quality Salamander brand shoes cost $93.16, compared with $60. A Siemens dishwasher costs $745.34, up from $480.

The $2.54 Big Mac is about $1 more than the same hamburger in Chicago. For a large Coke at a Frankfurt MacDonald's, the consumer must now pay $1.58, up from $1.02 two years ago, and a regular order of french fries is 93 cents, up from 60 cents.

West Germany's inflation rate in the past two years remained at almost zero, meaning that consumer-goods prices in German marks rose only slightly, if at all, in the same 24-month period.