"The fact is, they generally already own everything that they need, and have minimal expenses."
You hit the nail on the head, renosteinke. 99.9% of seniors have everything paid for, which is more than I can say for us "younger generation". When I first started contracting, I used to give a discount to seniors. Now they pay the same as everyone else.
The key is to be respectful and honest with them, do a good job, and then charge them your normal rate. Many of my best customers are seniors as they tend to pay right away, give repeat business and pass my name along to other potential clients. As a contractor you can fall onto some lean times where there is little income, yet seniors always have a regular pension cheque (or "check" for you Americans out there), and most time that money just gets deposited into their bank account.