I was in that situation with a textbook costing about twice that. Ended up borrowing from the library and digitizing it myself using a camera mounted on the back of a hardwood chair with the book lying flat on the ground. In hindsight it would have been good with a glass plate to press the pages, but I unwarped the pages automatically using some open source software. In the end it turned out quite good, but probably spent 6 hrs or something on the ordeal.