That would be very expensive compared to ikea.
Look at the very popular Lack table, it's made from cardboard hexagons with four pieces of wood-like thing in the corners to hold the legs. You can't make that yourself for cheap, and just the material cost in eg. wood, would be more expensive than the full table in ikea.
Otherwise, there are many youtube channels specializing in woodworking where you can learn all the basics to design your own furniture, but it won't be cheap.
Billy bookcases though are just slabs of laminated engineered wood cut to rectangular dimensions, drilled with precision positioned and sized holes, plus a stack of dowels and camlock fasteners.
That seems parameterizable.
It depends on your comparison; a Lack table is maybe an extreme example.
I say this because I’m currently working on a project to build a full kitchen’s worth of cabinet carcasses using good quality 19mm plywood, and I’m aiming for it to be cost neutral with Ikea’s kitchen cabinets, having sourced the plywood from a local DIY store. (Obviously ignoring the cost of my existing tools.)
Which is to say, if you could source plywood in volume (therefore cheaper per square meter) and amortise the cost of the CNC machine and other tools over time, I think it would be feasible to be close to cost competitive with IKEA‘s kitchens.
yeah, those cardboard tables.. I had to glue in 2-4 (5 by 10 cm) stringers and refix legs to them for it to hold a measly epson c8600 and even then it stands on wooden planks to distribute the load.
ikea is a great inspiration for making your own furniture and then a source for bearable spare parts.
People like to complain about it not being solid wood but the furniture from Ikea, such as Lack and Kallax is fit for purpose and remains a low price despite the cost of wood going up a lot. And what you can get at a similar price point from Wal-Mart in North America, or Conforama in Europe, is much much worse quality. Especially the veneer which holds up from Ikea but is more like wallpaper if you spend the same price somewhere else.