The only way you're going to get it done for free is to spin, felt or otherwise work it for yourself.
Yes, the mills charge a lot, proportionately more for small quantities. Have you had a look at the Natural Fibre Co website? They give you prices and plenty of advice about fleece and what you can do with it. You will also learn the correct terminology, how best to prepare a fleece for selling, showing or sending to the mill, what options you have for processing, such as carded to batts, carded to roving, spun to yarn, or spun then woven to throws, blankets.
Have a look through past posts on this topic in 'crafts' to see how others deal with this same subject.
For next year, if you are sending meat lambs off for slaughter in their first autumn, you can get the skins back, salt them, then send them off to be processed into gorgeous sheepskins.