Yes there is more internal mechanics that need to be perfect for a FFP scope. I am sure some of the swing to them adds a small amount but they have always been more expensive.

As to being too small at lowest power, most don't buy them to be used at lowest power. If you bought a 5-25x FFP scope to sue 5x a lot then you bought the wrong scope. The lower power is used for quick, close shots where you won't be using the reticle subtensions but just the basic crosshair. The same as with a SFP. Both have their places but you have to buy the right scope for the job at hand.

We talked about it a bit in our FFP vs SFP podcast - https://soundcloud.com/vortexnationpodcast/ep-09-ffp-vs-sfp (Also available on apple podcasts and other podcast platforms)

But yes there is a fairly significant difference in cost of manufacturing. The reticle is down inside the one-piece scope tube rather than up near the top where the tube meets the separate eyepiece (Like in a SFP scope). When the eyepiece is off, a SFP reticle is right there and can be installed, removed, aligned much more easily. When it's on the end of the erector unit and down inside the tube, that's just that much more time and care needed to install it, align it and make sure it's correct. FFP reticles are also always glass-etched reticles. Usually in a scope family where there is a SFP reticle and a FFP reticle, the SFP is probably also glass-etched, to be fair, but the FFP reticle would look pretty different than the SFP reticle if you held them in your hand - it needs to be done much smaller because it will go through the full magnification process in the erector unit unlike a SFP reticle which just meets up with the image after everything has been magnified - those don't need to be done so microscopically small. On top of that, FFP reticle usually have a lot more intricate features on them that need to be done to extreme precision, so it's just harder to make even the physical reticle itself.

All that adds up!