There are some excellent seeding machines on the market giving excellent results, but even the best seeder can give you a poor result if the critical point, sowing depth, is not followed correctly. Ideally your new pasture should be sown between 5 - 15mm to ensure you don’t sow the seeds too deep or shallow and risk a poor establishment by way of uneven germination. Rolling the paddock or using press wheels at the time of sowing will ensure good seed soil contact, and a more rapid and even germination.
The cost of seed is generally a fairly small proportion of the total cost of re-sowing a pasture, when you take into account costs such as fuel, fertiliser, etc. It is very important not to jeopardise this very important project by skimping on sowing rates. If you start off with a poor pasture, you will always have a poor pasture. If the cost of the project is of major concern to you then you should look at doing a smaller area well, rather than a larger area poorly.