In all the presentations of an FPTAS for Knapsack I've seen, it is asserted that the optimal value is at always at least the value of the maximum-valued item (e.g. here, slide 12, where we have $V \leq V^*$, where $V$ is the value of the maximum valued item and $V^*$ is the optimal solution.).
Why is that? I mean, we could have a knaspack problem with two items, one with value $10000$ and size $10000$, and one with value $1$ and size $1$, and for a knapsack capacity of $1$ clearly the optimal solution is $1$, but $V = 10000$, and $V^* < V$.