Simple compounds of boron used in soapmaking and household cleaning sell for order ~$1 per kg. If you can't make isotopically pure Boron 11 for under $10 per k

Simple compounds of boron used in soapmaking and household cleaning sell for order ~$1 per kg. If you can't make isotopically pure Boron 11 for under $10 per kg in bulk out of such products in far greater quantities than could ever be used in fusion, I would be very surprised.