yes and no. I spent 450 or so total on my 2.25" bb. I can get a pair of 3.5" springs for 250 or so, bam I have a 3.5" lift for a total of 700. Just depends on how you find things and how they come together. But yes you very well could spend say, 400 for a bb (bb kit, shocks included and then a new track bar front and sway bar links). Then when you go to 3.5 you would need new shocks, new rear track bar (dont use the drop brackets, they're crap) and LCA's if you wanted to do them (not required) and any steering parts and bushings that need to be replaced. here's how I did mine so you can see.
Rubicon Express 1600 and 1650 front and rear adjustable track bars. Good for 3-5" (I got both for a little over 200, hell of a deal)
Rubicon Express shocks. Travel length the same as what comes with their 3.5" kit
Jks quicker disconnects (not required but I like them so I got them on, otherwise you'll need new front sway bar links for proper lift height
Rubicon Express rear sway bar links for 2-4" of lift.
2.25" coil spacers
IRO rear post extensions (so I don't drop a coil)
Hockey puck bump stop extensions
(way cheaper and work just as well)
So for me, I could throw on 3.5" coils and be fine.
I could throw on a 4.5" lift with new coils, proper shocks (not sure if mine would be the proper length or not, would have to look at that) and some new CA's, lower for sure, upper if I wanted. (So for that say 800 bucks).
So it would be more expensive slightly in the long run, but not by much as I bought track bars that would go up through 5" of lift.
Up to you