2001 RX300 185000 miles and original owner.
In trying to resolve a similar problem with the high mount brake light over the past 6 months, I've found several other possible solutions. First after several replacement bulbs attempts, the high mount would not light. Ultimately, I found that the bulb socket was bad, a connector at the bottom was broken/missing. Finally found the part without having to buy the assembly - Pt # 90075-99005. Put a new led in, low and behold the light works! Except that the dashboard warning light didn't disappear as hoped/expected.
After reading the car's electrical system is 'sensitive' to the particular bulb, in this case a Sylvania 921, I put the OEM bulb in and now have an warning light free dash.
For all, good luck.