Buying Anthurium seeds is not easily done. There are many reasons of which the chief is the difficulty in causing a plant to produce the seeds in the first place. The second is purely economical.

There are growers in southern Florida who produce them all the time, BUT, they have spent a great deal of time and money learning how to produce them. The majority grow the seeds themelves to seedling and small plants and then sell them at a much greater profit.

Growers in Indonesia often offer extremely low prices for large quantities of seed. Selling them for such a price, even several dollars per seed, is not practical to the grower who makes a living producing plants. One small plant can be worth $20 or more. A rare one can be worth $100 or more. Please read this link and you'll understand the issue better.

Here is a link that might be useful: Why Anthurium seeds are not easily available.