Let x be the cost of one guitar string.
The cost of one guitar pick is x - 1 because they only cost $1 more than the guitar picks.
The total amount Patrick spent on guitar picks is 25 * (x - 1) = 25x - 25.
The total amount he spent on guitar strings is 25 * x.
The combined total cost is 25x - 25 + 25x = 50x - 25.
50x - 25 = 40.
50x = 40 + 25.
50x = 65.
x = 65 / 50.
x = <<65/50=1.30>>1.30. Answer: \boxed{1.30}.