Have you been asked for prototype?

As an experienced inventor, I must advise new inventor to proceed with prototype request carefully. You wan to know who is asking for prototype and why?
I had been asked for prototype from an invention company for 3 times. They looked at my invention ideas and told me they would need a prototype. I said no problem and turn around built one myself for them, for all 3 different ideas. And they took a look and said No on all 3 cases after they looked at my prototype, and their comments were like, this market doesn't need another one of these. Come on, they could have told me so after the looked at my drawing and before I built my prototype. Later on I found out they also have prototyping service. They just want to sell you their service, and not really interesting at your idea. So be very careful, don’t believe everything people tell you. Be aware of praises that came too easy, find a reputable reviewer… There are a lot of sharks out there, they all want your money but doesn’t really want to help you.

The photo is a working cupholder prototype, despite the look, it really work great.