It is definitely a challenge, but as prev EM / hiring manager of many iOS / Android devs it certainly isn't impossible. Not sure about large and expensive. Surprisingly most of my best devs were all inbound, not via recruiters. Felt recruiters usually wasted our time and small teams of native devs can get a lot more done than web teams (at least so it seems based on my subjective exp).
My previous company had probably well over a dozen web engineers and then for our mobile side we had a total of 3, myself included. We also often had to adapt designs ourselves and work with product to fix flows for native. But we still managed to keep up with web.
edit: and not "keep up with web" in the we are working 80 hour weeks type thing, very normal working hours, 9-5. Possibly more normal than the web team.
My previous company had probably well over a dozen web engineers and then for our mobile side we had a total of 3, myself included. We also often had to adapt designs ourselves and work with product to fix flows for native. But we still managed to keep up with web.
edit: and not "keep up with web" in the we are working 80 hour weeks type thing, very normal working hours, 9-5. Possibly more normal than the web team.