TPE (thermoplastic elastomer) is a solid mid-range frame material that offers good flexibility at a more affordable price point than TPU. For most skiers hitting resort slopes in normal winter conditions, TPE frames work just fine—they'll flex enough to conform to your face and feel comfortable under a helmet.
The main trade-off is that TPE can stiffen up a bit in extreme cold, typically below single-digit temperatures. If you regularly ski in bitter conditions or on windy summit days, that slight loss of flexibility might be noticeable compared to TPU, which stays pliable even in the coldest weather.
For casual to regular skiers who aren't pushing into extreme cold regularly, TPE frames offer a perfectly acceptable balance of comfort and value. Just avoid the rigid plastic frames found on budget goggles—those can crack and create painful pressure points when the temperature drops.