The pictures I've seen of Lane 1 balls (even Joe's that are cut in half) don't show that they use any more or less resin than most companies. There's a core, surrounded by filler, wrapped with a coverstock that's around a half-inch or so deep. Some companies use thinner shells, some thicker, but around 3/8" to 1/2" for the most part.
If you want a ball with a lot of resin (for whatever reason), look for balls that don't use a filler. Not many are like that nowadays. Dynothane's high-end balls except for their asymmetrics are core and cover only. Lanemasters balls are core and cover only. A lot (if not all) of Visionary's, many Storms, and the low-end Roto-grips are cover and core only. In Storm's and RG's cases, the balls without filler generally have very large cores (X-factors and Paradigms, Fire line, Planets). Other balls with more modestly sized cores have filler material.
I'm not 100% convinced that longevity is because there's so much resin. Brunswick makes (made) Lane 1 balls for a long time, and Lane 1 put PK18 and Activator on almost all of their balls for the past few years. PK18 and Activator are two of the longest lasting covers around, but there isn't any more on them than on original Big B equipment. Sounds like your pro shop is full of carp, or he just wants you to spend the extra money for Lane 1.
You could always ask why Lane 1 is more expensive in the Lane 1 forum, but I wouldn't do it.
SH