The right publisher for your book makes a difference for your readers and its accessibility. If you are in a university position, where you publish may be a factor for tenure and promotion. Some well-regarded university presses have open access options, and other newer open access options are also available.
List of compliant book publishers (OAPEN-UK, useful list of publishers that comply with the open access requirements of the European Research Council)
Open Access Books are downloaded, cited, and mentioned more than non-OA books (LSE Impact Blog post reporting: findings that OA books are, on average, downloaded seven times more, cited 50% more, and mentioned online ten times more.)
BPCs and CPCs are relatively new and publishers are still working on how to cover their publishing costs. The variance is even greater than with article processing charges. One recent study cites: €500 to €18,500 ($585 - $21,640) for BPCs.
A very selective listing: