Lynn, I bought one in June of 1965, and I paid $59.95 for it. Considering the number of times I took it apart (just to see how it works), I think it held up pretty well. This was a very rugged machine that achieved excellent results. BUT -- it's got some rubber belts and pinch roller, which will deteriorate in time. It also uses tubes, which would be hard to find. It would be hard to place a dollar value on the unit. I don't know how many collectors of mono 7" reel-to-reel tape recorders there are out there. Realistically, it probably isn't worth very much. Condition is an issue that dictates value.
Mine was used extensively, and it needs a belt and volume control. It's on my "to do" list, and it has been for about 20 years. It's probably worth more to me for its sentimental value than as a collectible, although it probably deserves a respectable burial.
My suggestion would be to price similar vintage reel-to-reel tape recorders on eBay for price, and guide yourself accordingly. Good luck!