People are waiting in line to purchase something at a counter.
People wait to make their purchases at the counter.
"To make purchases" is a rephrasing of "purchase something," and waiting in line is a specific way to wait.
exists e1 p1 x1 x2 x3.(Topic(e1,p1) & exists e2 x4 x5.(at(e2,x5) & n_counter(x5) & Theme(e2,x4) & Actor(e2,x1) & v_purchase(e2) & n_thing(x4)) & in(e1,x3) & n_line(x3) & Actor(e1,x2) & v_wait(e1) & n_people(x2) & n_people(x1))
exists e1 p1 x1 x2 x3.(n_counter(x3) & Topic(e1,p1) & Actor(e1,x1) & v_wait(e1) & exists e2.(Theme(e2,x2) & Actor(e2,x1) & v_make(e2) & at(x2,x3)) & n_purchase(x2) & of(x2,x1) & n_thing(x1) & n_people(x1))