Stay away from that bike shop. They are a bunch of thieves. Anyone who suggests you throw away the trike because of a broken chain probably does not want to work on a recumbent. By giving you a ridiculously high estimate they are telling you to get lost.

You can buy a quality KMC chain on eBay for under $20 with shipping included. Look at the cassette in the rear and count gears. That will tell you if it is an 8 speed system or 9 speed. Six to 8 speed systems use the same chain KMC X8.93 and the 9 speed system uses KMC X9.93. If you have the broken chain, count the number of links or measure the length. There are 12 links in a foot and the standard chain is 116 links. If it is longer than 8.3 feet, you need more than one chain. This is a company I have used in the past.


8 speed chain $11.65 https://www.ebay.com/itm/KMC-X8-93-6...f18e%7Ciid%3A1
9 speed chain $12.50 https://www.ebay.com/itm/KMC-X9-9-Sp...f18e%7Ciid%3A1

You would need a chain pin tool to shorten the chain if you need to do that.