There is currently no processor model 7700X3D.
You may be asking about a 7800X3D and if so, I would caution you to be very suspect about purchasing used or very low priced chips as there has been a rash of fakes being sold on alternative marketplaces due to the popularity of the processor and the shortage of the new 9800X3D.
Retailers are currently selling the 7800X3D for around $450 which is equal to its initial launch MSRP. If you are willing to wait until the 9800X3D stock replenishes and demand for the older part goes down the price may come down.
Alternately if there is a Microcenter near you, there is a 6-core 7600X3D chip that sells at only $300 which is a significant savings over the 7800X3D model. However it is a Microcenter only part.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT