If you and other locals are renting at that rate buy the Finishlynx. The bronze version is $7500, which isn't that bad as far as business purchases go, and if you can rent it out a dozen times you're laughing. You could also sell your professional timing services to other events, cycling or otherwise.
Factor in all the time you save picking places and the sale of a few cool bike-throw photo finish pictures I think you can see how the system makes sense.