Bonded VDSL2 / ADSL2+ Modems with 4 or more lines bonded

What options are out there to bond 4 or more DSL lines together? I know Positron has a 4 and 8 pair VDSL2 modem http://www.positronaccess.com/AK626LC.php Adtran has a 8 port VDSL2 modem https://portal.adtran.com/web/page/portal/Adtran/product/1172868F1/470 and an Adtran 12 port ADSL2+ modem https://portal.adtran.com/web/page/portal/Adtran/product/1172850G1/470 Actelis has a 8 pair VDS2 Modem: http://actelis.com/actelis-products/ethernet-access-devices/ml700/ Is there anyone else out there? The problem with all these solutions is they each cost over $1000, which is a lot considering 2 port bonded VDSL2 modems are in the $75-150 range. I know demand for these products is low, but still hoping there is an OEM version.