£1,000 or thereabouts is probably the current going rate for a brand new genuine 19” OEM Pretoria alloy for the Golf.
Best way to tell if a Pretoria advertised for sale is a genuine one or not is to ask to see the reverse side of the spokes to ensure the important identifying marks are there. The offset of a replica is also likely to be be slightly more aggressive than the offset of a genuine OEM Pretoria, and the OEM centre caps might not fit a replica Pretoria.
Bear in mind that OEM Prets were available for other VW models (e.g. T-Roc R, Passat) with a different offset to the Pretoria’s fitted to the Golf. There’s also an OEM 18” version that is available from VW’s accessories range, so it’s important to check that any Pretoria alloy advertised for sale had the correct part number and spec details for the Golf.
The genuine OEM 19” Pretoria for the Golf will include the following information stamped into the reverse side of the spokes;
VW Part no; 5G0601025AJ or 5G0601025CK
Size and offset; 8J x 19 ET50
Manufacturer - Borbet or BBS (probably Borbet, but BBS did make some of the early Pretoria’s for VW)
There’ll also be the VW logo, and (I think) a JWL test certification mark stamped into the back of the spokes.
I’m assuming you’re not interested in a refurbished alloy? If you are, always ask the seller to confirm it’s not suffered any structural damage / structural repairs. Also, the silver colour of the Golf’s Prets seems to be a difficult colour for many wheel refurb companies to get an accurate colour match on, so there’s a risk a refurbished wheel might not match the other wheels on your car.