I’m paying just under £30 a year membership on account of my academic associations; it’s usually a little higher. I’m also opting to pay £10 per month in order to reduce my excess in the event of an accident, but that’s not mandatory (or you can pay a little more and remove the excess completely). Each trip then costs me about £25 to £30, which “feels” expensive (based on my mental model that “it doesn’t cost £30 to get to Aylesbury and back!”), but of course I’m NOT having to pay for the other costs of running a car, such as owning, maintaining, taxing, MOTing, etc. Nor am I paying for fuel, as that’s all covered too.
If we divide the total cost (assuming the upper value of £30 each trip) by the number of college trips I expect to make over the academic year, we get a grand total of £34.17 per trip. It’s complicated, because if I were to take more trips, the average cost of each would decrease as the membership and insurance-reduction costs became a less-significant part of my outgoings… but then, if I were regularly driving twice or three times per week, then it might be worth me owning a car instead! Zipcar is the best-value solution for me specifically because I only travel once a week, or so, and it comes with a few extra perks (cars when I need them, where I need them; doing good for the environment; nice shiny new vehicles) to help make up for the few minor downsides (won’t be able to amass no-claims bonuses; could conceivably be unable to get a car when I want one).