T8 bulbs have a maximum length of 4 feet. If you have an eight foot light with lens that has two 8 foot bulbs you can replace it with an eight foot fixture with four, 4 foot bulbs for around $100. If you want an eight foot open bulb fixture with four 4 foot bulbs, it would cost around $60. These prices include the ballast.

The cost of the T8 bulbs is still under $3. T8 fixtures also come in four foot lengths. Currently, a magnetic ballast will run you in excess of $35, so it makes sense to upgrade to the new energy efficient electronic ballasts and/or fixtures, and T8 bulbs.