Plaid Cymru and the Tories tripled campaign spending on May's Welsh assembly election compared with 2003, according to the Electoral Commission.
Plaid and the Tories spent 57p per vote gained
Figures indicate Conservatives spent nearly £246,000 and Plaid just under £245,500 in the run-up to the poll.
The Liberal Democrat spending was around £240,000, £10,000 less than four years ago.
Labour figures are due later in the year because the party spent more than £250,000 on election activities.
The statistics do not include spending by individual candidates.
On election day Plaid Cymru gained three seats, the Conservatives one and Labour lost four of its AMs.
The Lib Dem group remained six strong.
After nine weeks of negotiations, Labour and Plaid eventually formed a coalition Welsh Assembly Government and the Conservatives became the official opposition.
Campaign spending includes expenditure on party political broadcasts, advertising, mail shots, manifestos, rallies and handling the media.
Based on the number of votes cast, it is possible to calculate how much the parties spent for every vote gained in May.
Plaid Cymru expenditure went up from 20p per vote won in 2003 to 57p in 2007.
The Conservatives also spent 57p per vote, compared with 24p four years ago.
Lib Dem spending dropped from £1.09 per vote to 92p per vote between 2003 and 2007.
Conservative assembly group leader Nick Bourne said running "the best funded election campaign" his party had fought in Wales was "more than justified by the results".
"Much of the money was raised in Wales specifically for the campaign", he said.
Plaid Cymru AM Dr Dai Lloyd said the party had run its "most professional" election campaign entirely from Welsh sources of funding.
"If you want a well run campaign you've got to spend the money," he said.
The Liberal Democrats stressed that fighting elections was about more than just cash.
A Welsh Lib Dem spokesperson called the efforts of party activists "priceless".
"What we were most pleased with at the election was the additional activity we were able to generate, particularly in seats like Newport East, Pontypridd, Ceredigion, Wrexham, all the Cardiff seats and the Swansea seats where we took a big step forward as the challengers to Labour," he said.