Will there also be a slower cheaper version possible of this?
No. The speed has nothing to do with the pricing. It simply only takes one or two weeks. The price is, compared to a normal rate, at least 200 to 300 Euro cheaper.
Besides that the source is 100 percent trustworthy and will provide detailed pictures and even videos of the cabs he is offering. You might also be able to request cabs but we have to talk about this in detail. I am pretty sure that, in such cases, the buyers would need to deposite some money in advance to make sure that the deal will take place for sure.