Hi, thank you for your question!
I don't mean to confuse you with another appraiser responding to your inquiry, however my answer is quite different from Glenda's. When pricing Lowrey organs it is important to understand how severely they depreciate in value. Lowrey is the only remaining home organ business in America, and through finance and trade-up programs they have, they are able to get existing owners to turn a small purchase into an eventual large one. Their top-tier organs sell new in the $80,000-$100-000 range. Though, after that, they decline in value at an enormous rate and owners are always surprised to hear the prices of their organs when selling used.
In regard to your organ, I believe you have the model number mixed up from what you typed. The model number for the Majesty organ was LX510 rather than L5510--I'm assuming just a typo. This model was produced at the very end of the 1990's and into the early 2000's. It was not the top of the line Lowrey offering--there were some more expensive full featured organs that had more bells and whistles including a more professional pedal board.
To get more specific, this organ from this era in excellent condition would be worth approximately $2,000-$4,500 depending on how you sold it. While Craigslist and eBay are good places to get information, they are not the only place. Dealers will sell organs for higher prices, though they will pay you less than they sell for as any business does. Here are some examples from Craigslist and eBay.
(note they say dealer said it was worth $6,500)
(note the two organs here are relisted several times with no buyers, even with a low selling price of under $2,000)
(I called this piano dealer who wouldn't tell me exactly what they sold it for, but approximated $4,000-$6,000. This price includes delivery, which is at least $500 in itself, and a warranty).
I give you those options to back up my appraisal of this organ in the $2,000-$4,500 range. If the dealer sells for $6,000 then he won't give you more than $3,000 for it. Many Lowrey dealers would accept it as a trade in, but likely only on another organ with high margins. A piano dealer may accept it as well, but likely wouldn't give you as much of a trade in value as a Lowrey organ dealer.
If you're looking to sell, I would advise talking to a local piano/organ dealer if you're willing to take $2,000-$3,000 on it. If you want to sell privately, Craigslist is your best option where you can offer it for a few thousand more and have a decent chance of selling it. Unfortunately, I would have to advise against most of the websites listed in your first appraisal. Most of those deal with ANTIQUES only and do not deal at all in keyboard instruments, especially modern electronic instruments. You might also try https://www.churchorgantrader.com/ if you want to appeal to a wider audience (as well as eBay). While this is not technically a church organ, some churches do use these types of instruments and they sell for less than conventional church organs.
I hope this advice is helpful and gives you an idea as to why I priced your instrument this way. Rest assured that my thousands of piano and organ appraisals have given me the knowledge and background to appropriately price your item. Best wishes!
Please select a rating before leaving--I aim for five stars! This is how the website credits me, an independent appraiser, for completing this for you. Thank you!