The statement that the offer price is always lower than the bid price is incorrect. In the foreign exchange market, the offer (or ask) price is always higher than the bid price. This difference, known as the bid-offer spread, is the profit margin for the dealer or broker facilitating the transaction. The bid price represents the highest price a buyer is willing to pay for a security, while the offer price is the lowest price at which a seller is willing to sell. The dealer or broker earns their profit from this spread, providing a service to other market participants by offering liquidity and facilitating transactions. Therefore, the offer price must always be higher than the bid price to compensate the dealer for their services and the risks they undertake in providing liquidity to the market.

Choice A is incorrect. The bid-offer spread is indeed the difference between the offer price and the bid price. This statement correctly defines what a bid-offer spread is in foreign exchange markets.

Choice B is incorrect. The statement that the bid-offer spread is larger for very large transactions in the FX market is also correct. Larger transactions often involve more risk and uncertainty, which can lead to a wider spread as dealers seek to protect themselves from potential losses.

Choice D is incorrect. As explained above, both choices A and B are correct statements about factors influencing the bid-offer spread in FX markets, so it cannot be true that none of these statements are correct.