"Broly, the Legendary Super Saiyan was born with a power level of 10,000. This is comparable to most Saiyan elite warriors!" - Original answer
"Actually, the last time a Power Level reading was given (in the same terms as Broly's was) was Frieza's 1,000,000 level." - Second answer
The highest power level recorded is in fact 150 000 000, given to Super Saiya-jin Goku. It is also one of the last power levels, beyond the 5 recorded for Trunks restraining his power.