If you think $20k is high, you're going to have a heart attack when you see the cost for 1/2 mile of multi-strand, single mode, buriable cable; plus cost to trench and terminate it. This is not something you can do yourself -- fiber termination takes a great deal of training and practice.
Wireless is still your best, cheaper, option. You can always cut down a line of trees. (same thing power companies do when they run a new line.) Play around with Ubiquiti's AirLink tool (here
) They sell 900MHz, 2.3,2.4,2.5,3, and 5 GHz systems. The last time I used it (a few weeks ago), it did not include the 2.4G RocketDish.