Agreed that Eurorack or modular synthesis isn't something that I would recommend for a beginner. Also agree that a Eurorack system _could_ be an overly expensive version of an existing fixed-architecture synthesizer.
Eurorack's potential, however, is a way to explore synthesis after you've learned the basics. It can be a very open playground to try synthesis ideas that may not be possible on a fixed-architecture system.
To lower the costs of Eurorack, one could buy modules from the used market or the DIY method and build from kits if they have experience with electronics. The DIY path may also lead one to designing and building original Eurorack modules. Learn about synthesis and electronics at the same time!
As the above post mentioned, VCV Rack which is a software emulation of Eurorack is a free way to see if modular synthesis is something that appeals. Other free software near-alternatives are Pure Data (https://puredata.info/) (sibling of the commercially available Max/MSP), Bespoke (https://www.bespokesynth.com/), and SunVox (https://warmplace.ru/soft/sunvox/).
It's worth noting that the price of an OP-1 was much lower when it initially launched. I bought mine directly from TE for $850 + shipping + import duties. A re-launch of the product bumped the price to where it is currently.
I also agree that the current price, while high, is not leagues above what other music gear is priced at. Take a single synthesizer, a sampler, add a keyboard, a sequencer, effects pedals, and a mixer and you can easily exceed $1000. The OP-1 has multiple synthesis engines, multiple sequencers, multiple effects, and sampling capabilities (you can even sample from FM radio, sound familiar?)
While the OP-1 may not win awards for any one of those features, it does unify all of them into a portable package. The OP-1 has also served as a gateway drug for me. I've since purchased even pricier synth gear :)
Indeed Teenage Engineering is a design studio which just happens to have some synthesizer products.
One of the TE founders, Jesper Kouthoofd, used to work with Elektron, a Swedish synthesizer firm. While there he designed the Machinedrum product's UI.