There's an old German proverb, "Alles ist seinen Preis wert." That means, "Everything is worth what its purchaser will pay for it."

Perhaps German pharmaceutical company Bayer AG should share that proverb with Monsanto, as Monsanto rejects their third buyout offer since May.

The German pharmaceutical and crop chemical company is now offering $65 million, or $127.50 a share to acquire Monsanto – a 2 percent increase on its previous offer of $125 a share.

Bayer has twice sweetened the deal for the St. Louis-based seed company, even throwing in a $1.5 billion antitrust breakup fee.

While that 2 percent increase didn't lead to a deal, it was enough for Monsanto at least agree to open its books to Bayer for due diligence checks on the business – a primary point of contention in the companies' past talks.

Analysts at brokerage Equinet say Bayer has now capped its Monsanto bid, and a higher bid could "imply a risk to Monsanto shareholders of either a hostile bid at a lesser consideration, or no deal at all."

John Bennett of fund manager Henderson said that he opposed the revised offer.

"Bayer have backed themselves into a corner," he said in emailed comments to Reuters. "The money would have been better spent buying their own stock. Alas, for shareholders, it was not to be."

Analysts from equity research firm Baasder-Helvea say they expect Monsanto to hold out for an offer for somewhere between $130 and $135 a share.

So will Bayer sweeten the deal again? A Monsanto board meeting next week may answer that question.

But for now, it seems Bayer will continue to abide by another German proverb that has stood the test of time: "Alles zu seiner Zeit," or "Patience is a virtue."

Read More:

• New Bayer Offer for Monsanto Triggers More Information Sharing (Wall Street Journal)
• Bayer sweetens Monsanto bid as talks enter final stretch (Reuters)