UPS billed me $1600 after purchase on reverb. Am I liable for this?

I’m looking for guidance on who is legally responsible for a large UPS charge.

I purchased a guitar on Reverb and paid a fixed $150 shipping fee at checkout. The listing showed the seller as located in Charlotte, NC. The guitar ultimately shipped from South Korea, and I was never informed during checkout or in the listing that this would be an international shipment.

After delivery, I received a UPS invoice for $1,632.57 with the following breakdown:

Freight: $1,238.51 (billed to receiver)

Declared Value Fee ($1,380.89): $23.80

Additional Handling Charge: $14.78

Fuel Surcharge: $352.98

I already paid import duties (~$36), which I understand and accept. I never agreed to any additional or post-delivery shipping charges beyond the $150 paid at checkout. The billed weight also appears to be significantly higher than the actual shipment weight (~60 lbs billed vs ~10–15 lbs actual).

Question:

Given these facts, am I (the buyer/receiver) legally responsible for these UPS charges, or should they fall on the shipper/seller or UPS?

Location: California.

Any guidance is appreciated.