I would give $50 for it no questions asked. It looks like an early second gen gun, it has the second gen style barrel and shroud at least. The early second gen guns have single trigger frames like this one and there should be a small red led on the bottom rear of the grip frame. Also the second gen guns had the select-fire board that ran off a single 9v not 4aa batteries as the previous did. I prefer the appearance of the first gen guns with the huge hard plastic hand-guard, but still like the second gens especially when they have a single trigger frame.
The value on these things is so inconsistent. Around February and March lots of people were looking for them, a POS of a Rainmaker in stock form sold as non working and in pieces went for $140 back then! But $100 to $130 was more common for a nice gun. I bought a like new in the box Rainmaker at the time for a little over $100. Then after 3 months nearly none of them showing up for sell on the usual sites a bunch were listed and the sellers had trouble moving them. One had lots of rare and desirable upgrades (well desirable to rainmaker fans) it only brought around $110~$120, and nice stock guns seemed to bring about $60 to $70 including the shipping but it would take a few weeks for them to sell.