I’ve seen that ad batted around with these same comments a few times over the years. I only really notice it because my first 22LR was an M99M1, the lower of the two rifles pictured.
The two common misconceptions:
1) Folks see the photo which LOOKS like an M1 Carbine, and see the word “Carbine” in the header and assume it’s an M1, then see the bold black “$49.99” at the bottom and can’t believe an M1 Carbine would have sold only a generation ago for so little. It’s misleading for sure - but it’s nothing more than an M99, the precursor to the M60 (or 795 in the case of the dbm model), with a shorter mag tube and a handguard on top. Price comparison with a cheap 22Lr rifle of today, not an expensive M1 Carbine or the modern replacement, the AR.
2) Folks don’t realize how quickly inflation works, and how dramatically so in the last generation or two. $49.95 in 1967 is $382.17 in 2019. Which puts the inflated price at over 100% more than the same action would cost on the street today. Minimum wage in 2019 is $12, whereas it was $1.40/hr in 1967. So it would have taken more than twice as many hours for a minimum wage worker to afford that Marlin in 1967 as it would today (~14hrs in 2019, vs. 35hrs in 1967, assuming $170 purchase price in 2019 and $50 in 1967).
Great rifles though: just like the model 60 or 795, but sexier, and without the last shot hold open. My Marlin M99M1 is on it’s 4th generation in my family. My grandpa bought it in ‘71 after he retired from the Navy, then gave it to my dad in ‘77. I received it in ‘89 as a birthday present, and gave it to my son last year (for future use, since he has 2 other 22LR rifles, and doesn’t yet fit the full stock on the heirloom). Ours has seen a lot of hard use - my dad lost the rear sight riding pasture with it on his saddle, and the front sight fell off while I was in high school. Just never had the need to replace the rear sight or re-solder the front for myself, as I shot just as well for my needs with or without. I did buy a new rear sight for my son, and have the front sight back on using a set screw - for now.