The Sonicare e-series basic model is still about $25.
Brought my 18 yr old daughter to the dentist, and once again, no cavities and no cleaning necessary. She doesn't floss, she only uses Sonicare.
As far as replacing heads - they have a reminder color that fades when it's time to replace. I don't skimp here - when the color has faded, or a few bristles have frayed, it's time to replace. Not worth it when it comes to my teeth.
I never viewed being sick as reason to replace heads, reason being the sonic waves kill bacteria. The same reason they knock out the plaque and toughen up your gums is the same reason any bacteria would not live on them.
Our local HEB had $13.00 off coupons for Sonicares over the holiday. So I got a couple more units for $12 bucks apiece.